Magnetoresistance element with increased operational range

ABSTRACT

A magnetoresistance (MR) element includes a first stack portion comprising a first plurality of layers including a first spacer layer having a first thickness and a first material selected to result in the first stack portion having a first sensitivity to the applied magnetic field. The MR element also has a second stack portion comprising a second plurality of layers, including a second spacer layer having a second thickness to result in the second stack portion having a second sensitivity to the applied magnetic field. The first thickness may be different than the second thickness resulting in the first sensitivity being different than the second sensitivity.

RELATED APPLICATIONS

This application is a CONTINUATION-IN-PART application under 37 C.F.R. §1.53(b)(2) and claims the benefit of and priority to U.S. patentapplication Ser. No. 15/600,186 (filed May 19, 2017), which isincorporated here by reference in its entirety.

BACKGROUND

As is known in the art, magnetic field sensing elements can be used in avariety of applications. In one example application, a magnetic fieldsensing element can be used to detect motion (e.g., rotation) of anobject, such as a gear or ring magnet. A magnetic field affected bymotion of the object may be detected by one or more magnetic fieldsensing elements, such as Hall effect elements and/or magnetoresistanceelements, which provide a signal (i.e., a magnetic field signal) inresponse to an applied magnetic field. Motion of the object may, forexample, result in variations in a distance between a perimeter of theobject (or target features of the object) and the magnetic field sensingelements, which may result in variations in the applied magnetic fieldto which the magnetic field sensing elements are exposed, and in themagnetic field signals provided by the magnetic field sensing elementsin response to the applied magnetic field. Such magnetic field signalscan be processed to detect position, proximity, speed and/or directionof motion of the object, for example.

Various parameters characterize the performance of magnetic fieldsensing elements and circuits or sensors that use magnetic field sensingelements. With regard to magnetic field sensing elements, the parametersinclude sensitivity, which corresponds to a change in a resistance of amagnetoresistance element or a change in an output voltage from a Halleffect element, for example, in response to an applied magnetic field(e.g., a magnetic field as may be affected by motion of a ferromagneticobject). Additionally, with regard to magnetic field sensing elements,the parameters include linearity, which corresponds to a degree to whichthe resistance of the magnetoresistance element or the output voltagefrom the Hall effect element varies linearly (i.e., in directproportion) to the applied magnetic field.

Magnetoresistance elements are known to have a relatively highsensitivity compared, for example, to Hall effect elements.Magnetoresistance elements are also known to have moderately goodlinearity, but over a restricted or limited range of magnetic fields,more restricted in range than a range over which Hall effect elementscan operate. It is known that in the restricted range of magnetic fields(i.e., in a so-called “linear region” or “linear range” of amagnetoresistance element), the resistance of a magnetoresistanceelement is typically indicative of an applied magnetic field to whichthe magnetoresistance element is exposed. It is also known that outsidethe restricted range of magnetic fields (i.e., in so-called “saturationregions”), the resistance of a magnetoresistance element is typicallynot indicative of the applied magnetic field. As a result of theforegoing, an operational range of a magnetoresistance element (i.e., arange in which the magnetoresistance element has a resistance that isindicative of an applied magnetic field) is typically limited to therestricted range of magnetic fields (i.e., the linear range of themagnetoresistance element). Additionally, an operational range of acircuit or sensor (e.g., a magnetic field sensor) using themagnetoresistance element (i.e., a range in which the circuit or sensorusing the magnetoresistance element is capable of generating a signalindicative of the applied magnetic field) may be limited to theoperational range of the magnetoresistance element.

For at least the above reasons, the fundamental usage for conventionalmagnetoresistance elements, and circuits or sensors using conventionalmagnetoresistance elements, has typically been limited to applicationsin which sensing is needed over a restricted range of magnetic fields(e.g., low strength magnetic fields) and the relatively high sensitivitycharacteristics of magnetoresistance elements are desired.

SUMMARY

In an embodiment, a magnetoresistance element deposited upon a substratecomprises a first stack portion comprising a first plurality of layers,wherein the first stack portion comprises a first spacer layer having afirst thickness and a first material selected to result in the firststack portion having a first sensitivity to the applied magnetic field;and a second stack portion comprising a second plurality of layers,wherein the second stack portion is disposed over the first stackportion, wherein the second stack portion has a second spacer layerhaving a second thickness and a second material selected to result inthe second stack portion having a second sensitivity to the appliedmagnetic field, wherein the first thickness is different than the secondthickness resulting in the first sensitivity being different than thesecond sensitivity.

In another embodiment, a magnetic field sensor comprises one or moremagnetoresistance elements deposited upon a substrate comprising a firststack portion comprising a first plurality of layers, wherein the firststack portion comprises a first spacer layer having a first thicknessand a first material selected to result in the first stack portionhaving a first sensitivity to the applied magnetic field; and a secondstack portion comprising a second plurality of layers, wherein thesecond stack portion is disposed over the first stack portion, andwherein the second stack portion has a second spacer layer having asecond thickness selected to result in the second stack portion having asecond sensitivity to the applied magnetic field, wherein the firstthickness is different than the second thickness resulting in the firstsensitivity being different than the second sensitivity.

In another embodiment, a magnetic field sensor comprises amagnetoresistance element configured to generate first and secondsubstantially linear responses to an applied magnetic field, wherein thefirst and second substantially linear responses have substantially zerooffset with respect to an expected response of the magnetoresistanceelement at an applied magnetic field strength of about zero Oersteds.

In another embodiment, a magnetic field sensor comprises means forgenerating first and second substantially linear responses to an appliedmagnetic field, wherein the first and second substantially linearresponses have substantially zero offset with respect to an expectedresponse at an applied magnetic field strength of about zero Oersteds

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the disclosure, as well as the disclosureitself may be more fully understood from the following detaileddescription of the drawings, in which:

FIG. 1 is a plot illustrating an example response characteristic of anideal prior art magnetoresistance element;

FIG. 2 is a block diagram showing layers of an example prior artmagnetoresistance element with a double pinned arrangement;

FIG. 3 is a plot illustrating example response characteristics of theprior art magnetoresistance element of FIG. 2;

FIG. 4 is a block diagram showing layers of another example prior artmagnetoresistance element with a dual double pinned arrangement;

FIG. 5 is a plot illustrating example response characteristics of theprior art magnetoresistance element of FIG. 4;

FIG. 6 is a plot illustrating response characteristics of an examplemagnetoresistance element according to the disclosure;

FIG. 7 is a block diagram showing layers of a first examplemagnetoresistance element with a dual double pinned arrangementaccording to the disclosure;

FIG. 8 is a block diagram showing layers of a second examplemagnetoresistance element with a dual double pinned arrangementaccording to the disclosure;

FIG. 9 is a block diagram showing layers of a third examplemagnetoresistance element with a dual single pinned arrangementaccording to the disclosure;

FIG. 10 is a plot illustrating first example response characteristics ofthe magnetoresistance element of FIG. 9;

FIG. 11 is a plot illustrating second example response characteristicsof the magnetoresistance element of FIG. 9;

FIG. 12 is a block diagram showing layers of a fourth examplemagnetoresistance element with a double and single pinned arrangementaccording to the disclosure;

FIG. 13 is a block diagram showing layers of a fifth examplemagnetoresistance element with a triple double pinned arrangementaccording to the disclosure;

FIG. 14 is a block diagram showing an example resistor dividerarrangement that may include magnetoresistance elements according to thedisclosure;

FIG. 14A is a block diagram of an example bridge arrangement that mayinclude magnetoresistance elements according to the disclosure; and

FIG. 15 is a block diagram of an example magnetic field sensor that mayinclude magnetoresistance elements according to the disclosure.

FIG. 16 is a block diagram showing layers of a double pinnedmagnetoresistance element.

FIG. 17 is a block diagram showing layers of a dual double pinnedmagnetoresistance element.

FIG. 18 is a graph of a transfer function of a magnetoresistanceelement.

FIG. 19 is a graph of transfer functions of magnetoresistance elements.

FIG. 20 is a graph of transfer functions of magnetoresistance elements.

DETAILED DESCRIPTION

The features and other details of the concepts, systems, and techniquessought to be protected herein will now be more particularly described.It will be understood that any specific embodiments described herein areshown by way of illustration and not as limitations of the disclosureand the concepts described herein. Features of the subject matterdescribed herein can be employed in various embodiments withoutdeparting from the scope of the concepts sought to be protected.Embodiments of the present disclosure and associated advantages may bebest understood by referring to the drawings, where like numerals areused for like and corresponding parts throughout the various views. Itshould, of course, be appreciated that elements shown in the figures arenot necessarily drawn to scale. For example, the dimensions of someelements may be exaggerated relative to other elements for clarity.

For convenience, certain concepts and terms used in the specificationare provided. As used herein, the term “magnetic field sensing element”is used to describe a variety of electronic elements that can sense amagnetic field. One example magnetic field sensing element is amagnetoresistance or magnetoresistive (MR) element. Themagnetoresistance element generally has a resistance that changes inrelation to a magnetic field experienced by the magnetoresistanceelement.

As is known, there are different types of magnetoresistance elements,for example, a semiconductor magnetoresistance element such as a giantmagnetoresistance (GMR) element, for example, a spin valve, a tunnelingmagnetoresistance (TMR) element, and a magnetic tunnel junction (MTJ).As used herein, the term “magnetoresistance element” may refer, withoutexclusivity, to any or all of these types of magnetoresistance elements.Depending on the device type and other application requirements,magnetoresistance elements may be a device made of a type IVsemiconductor material such as Silicon (Si) or Germanium (Ge), or a typeIII-V semiconductor material like Gallium-Arsenide (GaAs).

The magnetoresistance element may be a single element or, alternatively,may include two or more magnetoresistance elements arranged in variousconfigurations, e.g., a half bridge or full (Wheatstone) bridge.

As is known, magnetoresistance elements (e.g., GMR, TMR) tend to haveaxes of maximum sensitivity parallel to a substrate on which they areformed or otherwise provided.

As used herein, the term “magnetic field sensor” is used to describe acircuit that uses one or more magnetic field sensing elements, generallyin combination with other circuits. Magnetic field sensors are used in avariety of applications, including, but not limited to, an angle sensorthat senses an angle of a direction of a magnetic field, a currentsensor that senses a magnetic field generated by a current carried by acurrent-carrying conductor, a magnetic switch that senses the proximityof a ferromagnetic object, a motion (e.g., rotation) detector thatsenses passing ferromagnetic articles, for example, magnetic domains ofa ring magnet or features of a ferromagnetic target (e.g., gear teeth)where the magnetic field sensor is used in combination with aback-biased magnet or other magnet, and a magnetic field sensor thatsenses a magnetic field density of a magnetic field.

Referring to FIG. 1, a plot 100 shows a curve 102 (i.e., a transfercurve) representative of an example response characteristic of a priorart ideal magnetoresistance (MR) element as it is exposed to magneticfields of varying strengths. The magnetic fields may, for example, belocal and/or external magnetic fields (i.e., applied magnetic fields)which may be generated by one or more sources.

The plot 100 has a horizontal axis with a scale in magnetic fieldstrength units (e.g., Oersteds (Oe)) and a vertical axis with a scale inresistance units (e.g., Ohms (Ωs)). Positive magnetic field strengthunits (e.g., +X) may correspond to a magnetic field experienced by theMR element in a first direction. Additionally, negative magnetic fieldstrength units (e.g., −X) may correspond to a magnetic field experiencedby the MR element in a second direction that is opposite from the firstdirection.

As illustrated, the curve 102 has a linear region 102 a (i.e., a singlelinear region) between an upper saturation point 102 b and a lowersaturation point 102 c in which an electrical resistance of the MRelement characterized by curve 102 that generally changes linearly(i.e., in direct proportion) to changes in magnetic field strength ofthe magnetic field experienced by the MR element. In the linear region102 a, which corresponds to an operational range (or dynamic range) ofthe MR element, the resistance of the MR element is generally indicativeof the magnetic field strength of the magnetic field. Additionally, inthe linear region 102 a, a signal produced by a circuit or sensorincluding the MR element may also be indicative of the strength of themagnetic field. For the prior art ideal MR element, the linear region102 a of curve 102 is substantially centered about a crossing of thevertical and horizontal axes of plot 100, i.e., when the MR elementexperiences a nominal (or zero) magnetic field, the resistance of the ofthe MR element may be a value between that of the saturation regions 102d, 102 e in the plot shown, as indicated by point 102 f, and the MRelement is not subject to an offset error.

As also illustrated, the curve 102 has first and second so-called“saturation regions” 102 d, 102 e in which the resistance of the MRelement no longer changes (or changes very little) in response tochanges in the magnetic field and curve 102 correspondinglysubstantially levels off. A temporary large magnetic field experiencedby the MR element may, for example, saturate the MR element, and placethe MR element in one of the saturation regions 102 d, 102 e.

In saturation region 102 d in which the magnetic field has a negativemagnetic field strength (−X), for example, the resistance of the MRelement remains substantially constant at a maximum resistance value (orwithin a maximum resistance range). Additionally, in saturation region102 e in which the magnetic field has a positive magnetic field strength(+X), the resistance of the MR element remains substantially constant ata minimum resistance value (or within a minimum resistance range). Inother words, in the saturation regions 102 d, 102 e, the resistance ofthe MR element remains substantially constant independent of changes inthe magnetic field and the MR element has substantially no signalresponse. It follows that in the saturation regions 102 d, 102 e theresistance of the MR element is generally not indicative of the magneticfield strength of the magnetic field. Additionally, in the saturationregions 102 d, 102 e, a signal (e.g., an output signal) produced by acircuit or sensor including the MR element may also not be indicative ofthe magnetic field strength of the magnetic field. For example, thesignal produced by the circuit or sensor may be clipped on both sides ofthe linear region 102 a (i.e., in saturation regions 102 d, 102 e), orclipped on one side of the linear region 102 a (i.e., in eithersaturation region 102 d or 102 e) with an offset, and remainsubstantially constant independent of changes in the magnetic field insaturation regions 102 d, 102 e.

As a result of the foregoing, detection accuracy of the MR element andthe circuit or sensor may be substantially reduced when the MR elementis operating in the saturation regions 102 d, 102 e. It follows that theMR element and the circuit or sensor are typically limited to sensingmagnetic fields in the linear region 102 a over a restricted range ofmagnetic fields. For at least the above reason, it may be desirable toextend or increase the linear region 102 a (i.e., operational range) ofthe MR element and reduce or limit operation of the MR element in thesaturation regions 102 d, 102 e.

It is understood that the above-described linear region 102 a andsaturation regions 102 d, 102 e are representative of an ideal linearregion and ideal saturation regions, respectively, and the response ofreal MR elements (e.g., prior art MR element 200, shown in FIG. 2, asdiscussed below) may vary. For example, the linear region of a real(i.e., non-ideal) MR element is generally not perfectly linear.Additionally, real MR elements are also generally responsive totemperature changes and are subject to an offset error.

Referring to FIGS. 2-5, example prior art non-ideal MR elements (i.e.,real MR elements) and response curves associated with the prior art MRelements are shown. It should be appreciated that the example prior artMR elements described below are but several of many potentialconfigurations of prior art MR elements. Additionally, it should beappreciated that the example response curves described below are butseveral of many representative response curves of the prior art MRelements.

Referring now to FIG. 2, a first example prior art MR element 200 (e.g.,a so-called “double pinned MR element”) that is representative of a real(i.e., non-ideal) MR element, is deposited or otherwise provided upon asubstrate 201 (e.g., a Silicon substrate) and includes a plurality oflayers (here, twelve layers). The plurality of layers includes anonmagnetic seed layer 202 disposed over the substrate 201, a materialstack 210 (or stack portion) disposed over the nonmagnetic seed layer202 and a nonmagnetic cap layer 204 disposed over the material stack210.

The material stack 210 includes an antiferromagnetic pinning layer 211disposed over the nonmagnetic seed layer 202, a ferromagnetic pinnedlayer 212 disposed over the antiferromagnetic pinning layer 211, and anonmagnetic spacer layer 213 disposed over the ferromagnetic pinnedlayer 212. The material stack 210 also includes a free layer structure214 disposed over the nonmagnetic spacer layer 213, a nonmagnetic spacerlayer 215 disposed over the free layer structure 214 and a pinned layerstructure 216 disposed over the nonmagnetic spacer layer 215. The freelayer structure 214 includes a first ferromagnetic free layer 214 a anda second ferromagnetic free layer 214 b disposed over the firstferromagnetic free layer 214 a. Additionally, the pinned layer structure216 includes a first ferromagnetic pinned layer 216 a, a secondferromagnetic pinned layer 216 c, and a nonmagnetic spacer layer 216 bdisposed therebetween.

The material stack 210 additionally includes an antiferromagneticpinning layer 217 disposed over the pinned layer structure 216 and thecap layer 204 disposed over the pinning layer 217 (e.g., to protect theMR element 200).

Each of the plurality of layers in the prior art MR element 200 includesone or more respective materials (e.g., magnetic materials) and has arespective thickness, as shown. Materials of the layers are shown byatomic symbols. Additionally, thicknesses of the layers are shown innanometers (nm).

In general, magnetic materials can have a variety of magneticcharacteristics and can be classified by a variety of terms, including,but not limited to, ferromagnetic, antiferromagnetic, and nonmagnetic.Detailed descriptions of the variety of types of magnetic materials arenot made herein. However, let it suffice here to say, that aferromagnetic material (e.g., CoFe) is a material in which magneticmoments of atoms within the material tend to, on average, align to beboth parallel and in a same direction, resulting in a nonzero netmagnetic magnetization of the material. Additionally, a nonmagnetic ordiamagnetic material (e.g., Ta, Cu or Ru) is a material which tends topresent an extremely weak magnetization that is opposite andsubstantially proportional to a magnetic field to which the material isexposed, and does not exhibit a net magnetization. Further, anantiferromagnetic material (e.g., PtMn) is a material in which magneticmoments of atoms within the material tend to, on average, align to beparallel but in opposite directions, resulting in a zero netmagnetization.

Within some of the plurality of layers in prior art MR element 200,arrows are shown that are indicative of magnetization directions of thelayers when the MR element 200 experiences a nominal (or zero) appliedmagnetic field. Arrows coming out of the page are indicated as dotswithin circles and arrows going into the page are indicated as crosseswithin circles.

Detailed descriptions of the various magnetization directions are notmade herein. However, let it suffice here to say that, as is known inthe art, some MR elements (e.g., GMR and TMR elements) operate with spinelectronics (i.e., electron spins) where the resistance of the MRelements is related to the magnetization directions of certain layers inthe MR elements.

The MR element 200 has a maximum response axis to magnetic fields whichis parallel to a surface of the substrate 201 over which the MR element200 is deposited, as indicated by arrow 199. Additionally, the MRelement 200 has a resistance that changes in response to the appliedmagnetic field in a direction of the maximum response axis of the MRelement 200 over a limited range of magnetic field strengths, as shownin plot 300 of FIG. 3, as discussed below.

Referring now to FIG. 3, a plot 300 shows curves 302, 304 representativeof example response characteristics of the MR element 200 of FIG. 2 asit is exposed to magnetic fields of varying strengths in a directionparallel to the maximum response axis 199 of the MR element 200. Theplot 300 has a horizontal axis with a scale in magnetic field strengthunits (e.g., Oersteds (Oe)) and a vertical axis with a scale inresistance units (e.g., Ohms (Ωs)). Similar to plot 100 shown in FIG. 1,positive magnetic field strength units (e.g., +X) in plot 300 maycorrespond to a magnetic field experienced by the MR element 200 in afirst direction. Additionally, negative magnetic field strength units(e.g., −X) in plot 300 may correspond to a magnetic field experienced bythe MR element 200 in a second direction that is opposite from the firstdirection.

Curve 302 corresponds to a response characteristic of the MR element 200as it is exposed to a magnetic field that sweeps from a positivemagnetic field strength value (e.g., 500 Oe) to a negative magneticfield strength value (e.g., −450 Oe). Additionally, curve 304corresponds to a response characteristic of the MR element 200 as itexposed to a magnetic field that sweeps from a negative magnetic fieldstrength value (e.g., −450 Oe) to a positive magnetic field strengthvalue (e.g., 500 Oe).

As illustrated, the curves 302, 304 have a substantially linear region301 a (i.e., a single linear region) and first and second saturationregions 301 b, 301 c. In the linear region 301 a, which corresponds toan operational range of the MR element 200 characterized by curves 302,304, the MR element 200 has a resistance that generally changes inproportion to changes in magnetic field strength of the applied magneticfield, here over a magnetic field strength range 303 (e.g., from about−60 Oe to about 40 Oe). In other words, in the linear region 301 a, theMR element 200 has a substantially linear response (i.e., a singlesubstantially linear response) corresponding to the applied magneticfield within the magnetic field strength range 303.

Additionally, in the saturation regions 301 b, 301 c, which areseparated from each other by the substantially linear region 301 a, theresistance of the MR element 200 remains substantially constantindependent of changes in magnetic field strength of the appliedmagnetic field. In other words, in the saturation regions 301 b, 301 c,the MR element 200 has a resistance that is substantially unresponsiveto changes in magnetic field strength. In particular, in saturationregion 301 b, the resistance of the MR element 200 remains substantiallyconstant at a maximum resistance value (or within a maximum resistancerange). Additionally, in saturation region 301 c, the resistance of theMR element 200 remains substantially constant at a minimum resistancevalue (or within a minimum resistance range). It follows that in thesaturation regions 301 b, 301 c the resistance of the MR element 200 isgenerally not indicative of the magnetic field strength of the magneticfield. As a result of the foregoing, the prior art MR element 200 istypically limited to measuring or sensing the magnetic field in thelinear region 301 a over magnetic field strength range 303 (i.e., alimited range of magnetic fields), which limits magnetic field input.

As also illustrated, unlike curve 102 of the ideal MR element shown inFIG. 1, curves 302, 304 of the MR element 200 (i.e., a real MR element)are not symmetrical about a magnetic field of about zero Oersteds. Inparticular, curves 302, 304 are horizontally offset (i.e., notsubstantially centered) with respect to an intersection of the verticaland horizontal axes of plot 300, as indicated by arrow 305. It followsthat the linear region 301 a of MR element 200 is not symmetrical aboutthe magnetic field of about zero Oersteds and, thus, the range ofmagnetic field strengths to which the MR element 200 is responsive(here, range 303) is also offset. As a result of this offset, the MRelement 200 has a resistance which is offset with respect to an expectedresistance of the MR element 200 in the linear or operational range(i.e., linear region 301 a) of the MR element 200. Additionally, asignal (e.g., an output signal) generated by a circuit or a sensor inwhich the MR element 200 may be provided may be subject to an offseterror if the offset of the MR element 200 is not taken into account andcorrected (e.g., through offset correction circuitry in the circuit orsensor).

In general, the offset can be caused by design and manufacturingconstraints and defects in layers and/or materials which form the MRelement 200. As one example, the offset can be caused by a misalignmentof one or more portions (i.e., layers) of the pinned layer structure 216of MR element 200 with respect to one or more portions (i.e., layers) ofthe free layer structure 214 of MR element 200. The offset can also becaused by temperature excursions which may result in a change in aresponse of the MR element 200 at room temperature and/or magnetic fieldstrength variation. The effect of temperature can, for example, becharacterized as a temperature coefficient in units of resistance perdegree temperature.

Referring now to FIG. 4, a second example prior art MR element 400(e.g., a so-called “dual double pinned MR element”) is deposited orotherwise provided upon a substrate 401 and includes a plurality oflayers. The plurality of layers includes a nonmagnetic seed layer 402disposed over the substrate 401, a first material stack portion 410(also sometimes referred to herein as “a first stack portion”) disposedover the nonmagnetic seed layer 402 and an antiferromagnetic pinninglayer 420 disposed over the first material stack portion 410. The MRelement 400 also includes a second material stack portion 430 (alsosometimes referred to herein as “a second stack portion”) disposed overthe antiferromagnetic pinning layer 420 and a nonmagnetic cap layer 404disposed over the second material stack portion 430.

The first stack portion 410, which contains a similar ordering orarrangement of layers as the stack portion 210 of the prior art MRelement 200 of FIG. 2 (less a second antiferromagnetic pinning layer,e.g., 217, shown in FIG. 2), includes an antiferromagnetic pinning layer411 disposed over the nonmagnetic seed layer 402 and a ferromagneticpinned layer 412 disposed over the antiferromagnetic pinning layer 411.The first stack portion 410 also includes a nonmagnetic spacer layer 413disposed over the ferromagnetic pinned layer 412 and a free layerstructure 414 disposed over the nonmagnetic spacer layer 413. The freelayer structure 414 includes a first ferromagnetic free layer 414 a anda second ferromagnetic free layer 414 b disposed over the firstferromagnetic free layer 414 a.

The first stack portion 410 further includes a nonmagnetic spacer layer415 disposed over the free layer structure 414 and a pinned layerstructure 416 disposed over the nonmagnetic spacer layer 415. The pinnedlayer structure 416 includes a first ferromagnetic pinned layer 416 a, asecond ferromagnetic pinned layer 416 c and a nonmagnetic spacer layer416 b disposed therebetween.

The second stack portion 430, which is similar to the first stackportion 410 but includes layers that are in a substantially reverseorder or arrangement as the layers which are shown in first stackportion 410 with respect to the seed layer 402, includes a pinned layerstructure 431 disposed over the antiferromagnetic pinning layer 420, anonmagnetic spacer layer 432 disposed over the pinned layer structure431 and a free layer structure 433 disposed over the nonmagnetic spacerlayer 432. The pinned layer structure 431 includes a first ferromagneticpinned layer 431 a, a second ferromagnetic pinned layer 431 c and anonmagnetic spacer layer 431 b disposed therebetween. Additionally, thefree layer structure 433 includes a first ferromagnetic free layer 433 aand a second ferromagnetic free layer 433 b disposed over the firstferromagnetic free layer 433 a.

The second stack portion 430 also includes a nonmagnetic spacer layer434 disposed over the free layer structure 433, a ferromagnetic pinnedlayer 435 disposed over the nonmagnetic spacer layer 434 and anantiferromagnetic pinning layer 436 disposed over the ferromagneticpinned layer 435. A nonmagnetic cap layer 204 is disposed over theantiferromagnetic pinning layer 436.

Similar to prior art MR element 200 shown in FIG. 2, each of the layersin prior art MR element 400 includes one or more respective materials(e.g., magnetic materials) and has a respective thickness, as shown.Materials of the layers are shown by atomic symbols. Additionally,thicknesses of the layers are shown in nanometers.

Additionally, similar to prior art MR element 200 shown in FIG. 2,within some of the plurality of layers in prior art MR element 400,arrows are shown that are indicative of magnetization directions of thelayers when the MR element 700 experiences a nominal (or zero) appliedmagnetic field. Arrows coming out of the page are indicated as dotswithin circles and arrows going into the page are indicated as crosseswithin circles.

Detailed descriptions of the various magnetization directions are notmade herein. However, let it suffice here to say that, as is known inthe art, some MR elements (e.g., GMR and TMR elements) operate with spinelectronics (i.e., electron spins) where the resistance of the MRelements is related to the magnetization directions of certain layers inthe MR elements.

The MR element 400 has a maximum response axis to magnetic fields whichis parallel to a surface of the substrate 401 over which the MR element400 is deposited, as indicated by arrow 399. Additionally, the MRelement 400 has an electrical resistance that changes generally inproportion to an applied magnetic field in a direction of the maximumresponse axis of the MR element 400 over a limited range of magneticfield strengths, as shown in plot 500 of FIG. 5, as discussed below.

Referring now to FIG. 5, a plot 500 shows curves 502, 504 representativeof example response characteristics of the MR element 400 of FIG. 4 asit is exposed to magnetic fields of varying strengths in a transversedirection relative to the maximum response axis 399 of the MR element400. The plot 500 has a horizontal axis with a scale in magnetic fieldstrength units (e.g., Oersteds) and a vertical axis with a scale inresistance units (e.g., Ohms (Ωs)).

Curve 502 corresponds to a response characteristic of the MR element 400as it is exposed to a magnetic field that sweeps from a positivemagnetic field strength value (e.g., 550 Oe) to a negative magneticfield strength value (e.g., −450 Oe). Additionally, curve 504corresponds to a response characteristic of the MR element 400 as itexposed to a magnetic field that sweeps from a negative magnetic fieldstrength value (e.g., −450 Oe) to a positive magnetic field strengthvalue (e.g., 550 Oe).

As illustrated, the curves 502, 504 have a substantially linear region501 a (i.e., a single substantially linear region) and first and secondsaturation regions 501 b, 501 c. In the linear region 501 a, whichcorresponds to an operational range of the MR element 400 characterizedby curves 502, 504, the MR element 400 has a resistance that generallychanges in proportion to changes in magnetic field strength of theapplied magnetic field, here over a magnetic field strength range 503(e.g., from about −100 Oe to about 40 Oe). In other words, the MRelement 400 has a substantially linear response to the applied magneticfield in the linear region 501 a. As also illustrated, the MR element400 has a single sensitivity level (i.e., rate of change in resistance)in the linear region 501.

In the saturation regions 501 b, 501 c, the resistance of the MR element400 remains substantially constant independent of changes in magneticfield strength. In other words, the MR element 400 has a resistance thatis substantially unresponsive to changes in magnetic field strength inthe saturation regions 501 b, 501 c. In particular, in saturation region501 b, the resistance of the MR element 400 remains substantiallyconstant at a maximum resistance value (or within a maximum resistancerange). Additionally, in saturation region 501 c, the resistance of theMR element 400 remains substantially constant at a minimum resistancevalue (or within a minimum resistance range). It follows that since theresistance of the prior art MR element 400 is not indicative of themagnetic field in saturation regions, MR element 400 is limited tomeasuring or sensing the applied magnetic field in the linear region 501a over the magnetic field strength range 503 (i.e., a limited range ofmagnetic fields).

As is also illustrated, similar to curves 302, 304 of MR element 200(i.e., a non-ideal MR element) shown in FIG. 3, curves 502, 504 of MRelement 400 (i.e., also a real MR element) are not symmetrical about amagnetic field of about zero Oersteds. In particular, curves 502, 504are horizontally offset with respect to an intersection of the verticaland horizontal axes of plot 500, as indicated by arrow 505. It followsthat the linear region 501 a of MR element 400 is not symmetrical aboutthe magnetic field of about zero Oersteds and, thus, the range ofmagnetic field strengths to which the MR element 400 is responsive(here, range 503) is also offset, albeit less offset than curves 302,304 of MR element 200. As a result of this offset, the MR element 400has a resistance which is offset with respect to an expected resistanceof the MR element 400 in the linear or operational range (i.e., linearregion 501 a) of the MR element 400. Additionally, a signal (e.g., anoutput signal) generated by a circuit or a sensor in which the MRelement 400 may be provided may be subject to an offset error if theoffset of the MR element 400 is not taken into account and corrected(e.g., through offset correction circuitry in the circuit or sensor).

Referring to FIGS. 6-13, example embodiments of MR elements according tothe disclosure and response curves associated with MR elements accordingto the disclosure are shown. It should be appreciated that the exampleMR elements described below are but several of many potentialconfigurations of MR elements in accordance with the concepts, systems,circuits and techniques described herein. Additionally, it should beappreciated that the example response curves described below are butseveral of many representative response curves of the MR elements.

Referring now to FIG. 6, a plot 600 shows curves 602, 604 representativeof example response characteristics of an example MR element accordingto the disclosure, the structure of which MR element is describedfurther in connection with figures below. Curves 602, 604 correspond toresponse characteristics of the MR element (e.g., 700, shown in FIG. 7,with layer 713 of the MR element having a thickness of about 3.3 nm andlayer 734 of the MR element having a thickness of about 2.0 nm) as it isexposed to a magnetic field of varying strengths in a direction parallelto a maximum response axis of the MR element (e.g., 699, shown in FIG.7). It is understood that the applied magnetic field (e.g., a localand/or external magnetic field) may be generated in various ways, forexample, depending on the type of circuit or sensor in which the MRelement is provided and its application.

The plot 600 has a horizontal axis with a scale in magnetic fieldstrength units (e.g., Oersteds (Oe)) and a vertical axis with a scale inresistance units (e.g., Ohms (Ωs)). The plot 600 also includes lines606, 608, 610, 612, 614, 616 which are representative of boundaries ofvarious regions or sub-regions in which the MR element may operate.

In the illustrated embodiment, curves 602, 604 have a firstsubstantially linear region 601 a and a second substantially linearregion (here, a second substantially linear region including a pluralityof substantially linear sub-regions 601 b, 601 c, 601 d, 601 e) (e.g.,piecewise or discrete linear regions). Additionally, curves 602, 604have a first saturation region 601 f and a second saturation region 601g. The MR element characterized by curves 602, 604 has a respectiveresponse (or responses) to the magnetic field to which the MR element isexposed in each of the substantially linear and saturation regions.Additionally, each of the substantially linear and the saturationregions is associated with a particular magnetic field threshold, orrange of magnetic field strengths of the applied magnetic field.

In particular, in first substantially linear region 601 a, the MRelement has a first substantially linear response (i.e., experiences afirst substantially linear change in resistance (slope)) to the appliedmagnetic field over a first magnetic field strength range 603 a.Additionally, in the second substantially linear region (i.e.,sub-regions 601 b, 601 c, 601 d, 601 e), the MR element has a secondsubstantially linear response (or responses) to the applied magneticfield over a second magnetic field strength range (i.e., sub-ranges 603b, 603 c, 603 d, 603 e). Further, in first and second saturation regions601 f, 601 g, the MR element has substantially no response to theapplied magnetic field over third and fourth magnetic field strengthranges 603 f, 603 g, i.e., the MR element is saturated and theresistance of the MR element no longer changes (or changes very little)in response to changes in the magnetic field.

In embodiments, the MR element also has a respective substantiallylinear response in each of the sub-regions 601 b, 601 c, 601 d, 601 e ofthe second substantially linear region, with the substantially linearresponses of the MR element in the sub-regions 601 b, 601 c, 601 d, 601e comprising the second substantially linear response of the secondsubstantially linear region. In particular, in sub-region 601 b, the MRelement may have a fifth substantially linear response to the appliedmagnetic field over sub-range 603 b of the second magnetic fieldstrength range. Additionally, in sub-region 601 c, the MR element mayhave a sixth substantially linear response to the applied magnetic fieldover sub-range 603 c of the second magnetic field strength range.Additionally, in sub-region 601 d, the MR element may have a seventhsubstantially linear response to the applied magnetic field oversub-range 603 d of the second magnetic field strength range. Further, insub-region 601 e, the MR element may have an eighth substantially linearresponse to the applied magnetic field over sub-range 603 e of thesecond magnetic field strength range.

In embodiments, each of the substantially linear responses (e.g., fifth,sixth, seventh, etc.) of the various sub-regions 601 b, 601 c, 601 d,601 e in the second substantially linear region of the MR element aredifferent from each other. Additionally, in embodiments, two or more ofthe substantially linear responses of the sub-regions 601 b, 601 c, 601d, 601 e are the same as or similar to each other. For example, inembodiments, the fifth and sixth substantially linear responses of theMR element may be the same as or similar to each other, but differentthan the seventh substantially linear response of the MR element.Additionally, in embodiments, the seventh and eighth substantiallylinear responses of the MR element may be the same as or similar to eachother, but different than the fifth and sixth substantially linearresponses of the MR element.

As illustrated, sub-region 601 b of the second substantially linearregion is contiguous with sub-region 601 d of the second substantiallylinear region. Additionally, sub-region 601 c of the secondsubstantially linear region is contiguous with sub-region 601 e of thesecond substantially linear region. However, sub-regions 601 b, 601 dare non-contiguous with sub-regions 601 c, 601 e. It follows that in theillustrated embodiment the second substantially linear region includes aplurality of non-contiguous sub-regions. It is understood that in otherembodiments the second substantially linear region may include aplurality of contiguous sub-regions (or a single sub-region).

As also illustrated, the MR element characterized by curves 602, 604 hasan associated sensitivity level (or levels) to the applied magneticfield in each of the substantially linear regions and the saturationregions. As discussed above, with regard to MR elements, sensitivitycorresponds to a change in the resistance of an MR element in responseto an applied magnetic field. In embodiments, the respective responses(e.g., first, second, third, etc. substantially linear responses) of theMR element to the magnetic field result in the MR element having thesensitivity levels.

In particular, in first substantially linear region 601 a, the MRelement has a first sensitivity level (i.e., a first rate of change inresistance) to changes in magnetic field strength of the appliedmagnetic field over the first magnetic field strength range 603 a.Additionally, in the second substantially linear region (i.e.,sub-regions 601 b, 601 c, 601 d, 601 e), the MR element has a secondsensitivity level to changes in magnetic field strength of the appliedmagnetic field over the second magnetic field strength range (i.e.,sub-ranges 603 b, 603 c, 603 d, 603 e). Further, in first and secondsaturation regions 601 f, 601 g, the MR element has third and fourthrespective sensitivity levels to changes in magnetic field strength ofthe applied magnetic field over third and fourth magnetic field strengthranges 603 f, 603 g.

In embodiments, the MR element also has a respective sensitivity levelto changes in magnetic field strength of the applied magnetic field ineach of the sub-regions 601 b, 601 c, 601 d, 601 e of the secondsubstantially linear regions, with the sensitivity levels of the MRelement in the sub-regions 601 b, 601 c, 601 d, 601 e comprising thesecond sensitivity level of the second substantially linear region. Inparticular, in sub-region 601 b, the MR element may have a fifthsensitivity level to changes in magnetic field strength of the appliedmagnetic field over sub-range 603 b of the second magnetic fieldstrength range. Additionally, in sub-region 601 c, the MR element mayhave a sixth sensitivity level to changes in magnetic field strength ofthe applied magnetic field over sub-range 603 c of the second magneticfield strength range. Additionally, in sub-region 601 d, the MR elementmay have a seventh sensitivity level to changes in magnetic fieldstrength of the applied magnetic field over sub-range 603 d of thesecond magnetic field strength range. Further, in sub-region 601 e, theMR element may have an eighth sensitivity level to changes in magneticfield strength of the applied magnetic field over sub-range 603 e of thesecond magnetic field strength range.

In embodiments, the first magnetic field strength range 603 a associatedwith first substantially linear region 601 a corresponds to relatively“low” strength applied magnetic fields (here, between about −20 Oe and+20 Oe). Additionally, in embodiments, magnetic field strengthsub-ranges 603 b, 603 c associated with sub-regions 601 b, 601 c of thesecond substantially linear region, respectively, correspond torelatively “medium” strength magnetic fields that are greater inmagnetic field strength than “low” strength magnetic fields associatedwith the first magnetic field strength range 603 a of firstsubstantially linear region 601 a. In the illustrated embodiment,magnetic field strength sub-range 603 b comprises negative magneticfield strength values (here, between about −20 Oe and about −120 Oe) andmagnetic field strength sub-range 603 c comprises positive magneticfield strength values (here, between about 20 Oe and about 125 Oe).

Additionally, in embodiments, the magnetic field strength sub-ranges 603d, 603 e associated with sub-regions 601 d, 601 e of the secondsubstantially linear region, respectively, correspond to relatively“high” strength magnetic fields that are greater in magnetic fieldstrength than the “medium” strength magnetic fields associated withmagnetic field strength sub-ranges 603 b, 603 c of sub-regions 601 b,601 c of the second substantially linear region. In embodiments, the“high” strength magnetic fields are not large enough to saturate the MRelement. In the illustrated embodiment, the magnetic field strengthsub-range 603 d comprises negative magnetic field strength values (here,between about −120 Oe and about −430 Oe) and magnetic field strengthsub-range 603 e comprises positive magnetic field strength values (here,between about 125 Oe and about 550 Oe).

Further, in embodiments, the third and fourth magnetic field strengthranges 603 f, 603 g associated with saturation regions 601 f, 601 g,respectively, correspond to magnetic fields that are greater in magneticfield strength than the “high” strength magnetic fields associated withmagnetic field strength sub-ranges 603 d, 603 e of sub-regions 601 d,601 e of the second substantially linear region. The magnetic fieldsassociated with the third and fourth magnetic field strength ranges 603f, 603 g, unlike the magnetic fields associated with the magnetic fieldstrength sub-ranges 603 d, 603 e of the second magnetic field strengthrange, are large enough to saturate the MR element such that theresistance of the MR element remains substantially constant in thepresence of changes in the applied magnetic field. In the illustratedembodiment, the magnetic field strength range-range 603 f comprisesnegative magnetic field strength values (here, between about −430 Oe andlarger) and magnetic field strength sub-range 603 g comprises positivemagnetic field strength values (here, between about 550 Oe and larger).

In the example embodiment shown, the first sensitivity level of the MRelement in first substantially linear region 601 a is different than(here, greater than) the second sensitivity level of the MR element inthe second substantially linear region (i.e., sub-regions 601 b, 601 c,601 d, 601 e). Additionally, the second sensitivity level of the MRelement in the second substantially linear region is different than(here, greater than) the third and fourth sensitivity levels of the MRelement in saturation regions 601 f, 601 g.

Further, in the example embodiment shown, the fifth and sixthsensitivity levels of the MR element in sub-regions 601 b, 601 c of thesecond substantially linear region are different than (here, greaterthan) the seventh and eighth sensitivity levels of the MR element insub-regions 601 d, 601 e of the second substantially linear region.Further, the seventh and eighth sensitivity levels of the MR element insub-regions 601 d, 601 e of the second substantially linear region aredifferent than (here, greater than) the third and fourth sensitivitylevels of the MR element in saturation regions 601 f, 601 g.

In other words, the MR element characterized by curves 602, 604 is moreresponsive (i.e., experiences a greater change in resistance, and has ahigher sensitivity) to applied magnetic fields in the first magneticfield strength range 603 a associated with first substantially linearregion 601 a than it is to applied magnetic fields in the secondmagnetic field strength range (i.e., sub-ranges 603 b, 603 c, 603 d, 603e) associated with the second substantially linear region (i.e.,sub-regions 601 b, 601 c, 601 d, 601 e). Additionally, the MR element ismore responsive to applied magnetic fields in the second magnetic fieldstrength range than it is to applied magnetic fields in the third andfourth magnetic field strength ranges 603 f, 603 g associated withsaturation regions 601 f, 601 g.

Further, in the example embodiment shown, the MR element is moreresponsive to applied magnetic fields in the sub-ranges 603 b, 603 cassociated with sub-regions 601 b, 601 c of the second substantiallylinear region than it is to applied magnetic fields in sub-ranges 603 d,603 e associated with sub-regions 601 d, 601 e of the secondsubstantially linear region. Further, the MR element is more responsiveto applied magnetic fields in the sub-ranges 603 d, 603 e associatedwith sub-regions 601 d, 601 e of the second substantially linear regionthan it is to applied magnetic fields in the third and fourth magneticfield strength ranges 603 f, 603 g associated with saturation regions601 f, 601 g.

In embodiments, the first substantially linear response of the MRelement in first substantially linear region 601 a corresponds to asubstantially linear response of a selected stack portion of the MRelement. For example, the first substantially linear response maycorrespond to a substantially linear response of a second stack portion(e.g., 730, shown in FIG. 7) of the MR element. Similarly, inembodiments, the second substantially linear response of the MR elementin the second substantially linear region (i.e., sub-regions 601 b, 601c, 601 d, 601 e) may correspond to a substantially linear response of asecond stack portion (e.g., 730, shown in FIG. 7) of the MR element.

Additionally, in embodiments, the first substantially linear response ofthe MR element in first substantially linear region 601 a corresponds toa substantially linear response of a selected stack portion of the MRelement, but with other stack portions of the MR element alsocontributing to the first substantially linear response. For example,the first substantially linear response may correspond to asubstantially linear response of a second stack portion (e.g., 730,shown in FIG. 7) of the MR element, but with a first stack portion(e.g., 710, shown in FIG. 7) of the MR element also contributing to atleast a portion of the first substantially linear response. Similarly,in embodiments, the second substantially linear response of the MRelement in the second substantially linear region (i.e., sub-regions 601b, 601 c, 601 d, 601 e) may correspond to a substantially linearresponse of the first stack portion of the MR element, but with thesecond stack portion of the MR element also contributing to at least aportion of the second substantially linear response. The foregoing may,for example, be due to the second stack portion still being responsiveto applied magnetic fields over the first magnetic field strength range603 a associated with the first substantially linear region 601 a, butwith a sensitivity level that is substantially reduced compared to asensitivity level of the second stack portion over the second magneticfield strength range (i.e., sub-ranges 603 b, 603 c, 603 d, 603 e)associated with the second substantially linear region (i.e.,sub-regions 601 b, 601 c, 601 d, 601 e).

The first substantially linear region 601 a and the second substantiallylinear region (i.e., sub-regions 601 b, 601 c, 601 d, 601 e) correspondto an operational range of the MR element characterized by curves 602,604 in the illustrated embodiment. In other words, the operational rangeof the MR element, which corresponds to a range of magnetic fields inwhich the MR element has a resistance that is indicative of a magneticfield strength of the magnetic field to which the MR element is exposed,includes a plurality of substantially linear regions (e.g., piecewise ordiscrete linear regions). Each of the substantially linear regions has arespective substantially linear response to the applied magnetic field,as discussed above. This is in contrast the prior art MR elementsdiscussed in connection with figures above (e.g., 400, shown in FIG. 4),which have an operational range with a single substantially linearregion and a single substantially linear response over the substantiallylinear region. One example result of the foregoing is the operationalrange of the MR element characterized by curves 602, 604 may have anincreased operational range compared, for example, to an operationalrange of the prior art MR elements, particularly where clipping mayoccur at much larger magnetic field strength levels of an appliedmagnetic field.

Another example result of the foregoing is that the operational range ofthe MR element characterized by curves 602, 604 includes a plurality ofsensitivity levels corresponding to the plurality of substantiallylinear responses of the MR element. This may, for example, provide forthe MR element having a first sensitivity level at relatively “low”strength fields (e.g., where SNR is relatively “low”) and a secondsensitivity level that is different than the first sensitivity level atmagnetic fields that are greater than the “low” strength magnetic fields(e.g., where SNR is relatively “high”), but not in saturation.

In embodiments, the sensitivity levels (e.g., first, second, third,etc.) and/or magnetic field strength ranges (e.g., first, second, third,etc.) associated with each of the above-described substantially linearregions and saturation regions may be adjusted through selection of oneor more characteristics (e.g., construction and/or dimensions) of the MRelement characterized by curves 602, 604, as described further inconnection with figures below.

Referring now to FIG. 7, a first example magnetoresistance (MR) element700 according to the disclosure is shown. The MR element 700 isdeposited upon a substrate 701 (e.g., a Si Substrate) and includes afirst material stack portion (also sometimes referred to herein as “afirst stack portion”) 710 and a second material stack portion (alsosometimes referred to herein as “a second stack portion”) 730. The firststack portion 710 has first and second opposing surfaces, with the firstsurface of the first stack portion 710 disposed over a seed layer 702(e.g., a non-magnetic seed layer) and the seed layer 702 disposedbetween the first stack portion 710 and the substrate 701. Additionally,the second stack portion 730 has first and second opposing surfaces,with the first surface of the second stack portion 730 disposed over apinning layer 720 (e.g., an antiferromagnetic pinning layer) and thepinning layer 720 disposed between the second stack portion 730 and thefirst stack portion 710. A cap layer 704 (e.g., a non-magnetic caplayer) is disposed over the second surface of the second stack portion730.

The first stack portion 710, which has a first substantially linearresponse corresponding to an applied magnetic field over a firstmagnetic field strength range, as discussed further below, includes afirst plurality of layers (here, 9 layers). The first plurality oflayers includes a pinning layer 711, a pinned layer 712 and a spacerlayer 713. The first stack portion 710 also includes a first free layerstructure 714, a spacer layer 715 and a pinned layer structure 716. Thefirst free layer structure 714 includes a first free layer 714 a and asecond free layer 714 b. Additionally, the pinned layer structure 716includes first pinned layer 716 a, second pinned layer 716 c and spacerlayer 716 b.

The pinning layer 711 is disposed over the seed layer 702 and the pinnedlayer 712 is disposed over the pinning layer 711. Additionally, thespacer layer 713 is disposed over the pinned layer 712 and the freelayer structure 714 is disposed over the spacer layer 713. Further, thespacer layer 715 is disposed over the free layer structure 714 and thepinned layer structure 716 is disposed over the spacer layer 715.

In embodiments, pinning layer 711 may be an antiferromagnetic pinninglayer and pinned layer 712 may be a ferromagnetic pinned layer, andspacer layer 713 may be a nonmagnetic spacer layer. Additionally, inembodiments, spacer layer 715 may be a nonmagnetic spacer layer andpinned layer structure 716 may include a synthetic antiferromagnetic(SAF) pinned layer structure or layer. First free layer 714 a of freelayer structure 714 may be a ferromagnetic free layer and second freelayer 714 b of free layer structure 714 may be a ferromagnetic freelayer. Additionally, first pinned layer 716 a of pinned layer structure716 may be ferromagnetic pinned layer, second pinned layer 716 c ofpinned layer structure 716 may be a ferromagnetic pinned layer, andspacer layer 716 b of pinned layer structure 716 may be a nonmagneticspacer layer. In embodiments, at least one of first pinned layer 716 aor second pinned layer 716 c comprises a same or similar material assecond free layer 714 b.

In the illustrated embodiment, pinning layer 711 is shown as includingPtMn or IrMn and pinned layer 712 is shown as including CoFe.Additionally, spacer layer 713 is shown as including Ru, first freelayer 714 a is shown as including NiFe and second free layer 714 b isshown as including CoFe. Further, spacer layer 715 is shown as includingCu, first pinned layer 716 a is shown as including CoFe, spacer layer716 b is shown as including Ru and second pinned layer 716 c is shown asincluding CoFe. However, it is understood that each of theabove-described layers in the first stack portion 710 may includematerials, or compositions of materials, that are different than thatwhich is shown, as described further below.

In the illustrated embodiment, pinning layer 711 is also shown as havinga thickness between about 5 nm and about 15 nm and pinned layer 712 isshown as having a thickness of about 2.1 nm. Additionally, spacer layer713 is shown as having a thickness of about 3.3 nm, first free layer 714a is shown as having a thickness of about 5 nm and second free layer 714b is shown as having a thickness of about 1 nm. Further, spacer layer715 is shown as having a thickness of about 2.4 nm, first pinned layer716 a is shown as having a thickness of about 2.1 nm, spacer layer 716 bis shown as having a thickness of about 0.85 nm and second pinned layer716 c is shown as having a thickness of about 2.0 nm. However, it isunderstood that each of the above-described layers may have a layerthickness that is different than that which is shown, as describedfurther below.

The second stack portion 730, which has a second substantially linearresponse that is different than the first substantially linear responseof the first stack portion 710, as discussed further below, includes asecond plurality of layers (here, 9 layers), i.e., a same number oflayers as the first plurality of layers of first stack portion 710 inthe illustrated embodiment. The second plurality of layers includes apinned layer structure 731, a spacer layer 732 and a free layerstructure 733. The second plurality of layers also includes a spacerlayer 734 and a pinned layer 735. The pinned layer structure 731includes a first pinned layer 731 a, a second pinned layer 731 c and aspacer layer 731 b. Additionally, the free layer structure 733 includesa first free layer 733 a and a second free layer 733 b.

The pinned layer structure 731 is deposited over the pinning layer 720and the spacer layer 732 is disposed over the pinned layer structure731. Additionally, the free layer structure 733 is disposed over thespacer layer 732 and the spacer layer 734 is disposed over the freelayer structure 733. Further, the pinned layer 735 is disposed over thespacer layer 734 and the pinning layer 736 is disposed over the pinnedlayer 735.

In embodiments, the pinned layer structure 731 may include an SAF pinnedlayer structure or layer and the spacer layer 732 may be a nonmagneticspacer layer. Additionally, in embodiments, the first pinned layer 731 aof pinned layer structure 731 may be ferromagnetic pinned layer, thesecond pinned layer 731 c of pinned layer structure 731 may be aferromagnetic pinned layer, and the spacer layer 731 b of pinned layerstructure 731 may be a nonmagnetic spacer layer. Further, inembodiments, the first free layer 733 a of free layer structure 733 maybe a ferromagnetic free layer and the second free layer 733 b of freelayer structure 733 may be a ferromagnetic free layer. In embodiments,the spacer layer 734 may be a nonmagnetic spacer layer, the pinned layer735 may be a ferromagnetic pinned layer and the pinning layer 736 may bean antiferromagnetic pinning layer.

In the illustrated embodiment, the first pinned layer 731 a is shown asincluding CoFe, spacer layer 731 b is shown as including Ru and thesecond pinned layer 731 c is shown as including CoFe. Additionally,spacer layer 732 is shown as including Cu, first free layer 733 a isshown as including CoFe and second free layer 733 b is shown asincluding NiFe. Further, spacer layer 734 is shown as including Ru,pinned layer 735 is shown as including CoFe and pinning layer 736 isshown as including PtMn or IrMn. However, similar to the layers in thefirst stack portion 710 of MR element 700, it is understood that each ofthe above-described layers in the second stack portion 730 of MR element700 may include materials, or compositions of materials, that aredifferent than that which is shown, as will be described further below.

In the illustrated embodiment, the first pinned layer 731 a is shown ashaving a thickness of about 2.0 nm, spacer layer 731 b is shown ashaving a thickness of about 0.85 nm, and the second pinned layer 731 cis shown as having a thickness of about 2.1 nm. Additionally, spacerlayer 732 is shown as having a thickness of about 2.4 nm, first freelayer 733 a is shown as having a thickness of about 1 nm and second freelayer 733 b is shown as having a thickness of about 5.0 nm. Further,spacer layer 734 has a thickness T1 in one of four example ranges, e.g.,about 1.6 nm to about 1.8 nm, about 2.2 nm to about 2.4 nm, about 2.9 nmto about 3.1 nm, or about 3.5 nm to about 3.7 nm. As one example, spacerlayer 734 may have a thickness T1 of about 2.0 nm. Additionally, pinnedlayer 735 is shown as having a thickness of about 2.1 nm and pinninglayer 736 is shown as having a thickness of between about 5 nm and about15 nm. However, similar to the layers in the first stack portion 710 ofMR element 700, it is understood that each of the above-described layersin the second stack portion 730 of MR element 700 may have a layerthickness that is different than that which is shown, as describedfurther below.

Within some of the plurality of layers in MR element 700, arrows areshown that are indicative of magnetization directions of the layers whenthe MR element 700 experiences a nominal (or zero) applied magneticfield. Arrows coming out of the page are indicated as dots withincircles and arrows going into the page are indicated as crosses withincircles.

Detailed descriptions of the various magnetization directions are notmade herein. However, let it suffice here to say that, as is known inthe art, some MR elements (e.g., GMR and TMR elements) operate with spinelectronics (i.e., electron spins) where the resistance of the MRelements is related to the magnetization directions of certain layers inthe MR elements.

The MR element 700 has a maximum response axis to magnetic fields whichis parallel to a surface of the substrate 701 over which the MR element700 is deposited, as indicated by arrow 699.

As noted above, the first stack portion 710 of MR element 700 has afirst substantially linear response corresponding to an applied magneticfield over a first magnetic field strength range. Additionally, as notedabove, the second stack portion 730 has a second substantially linearresponse that is different than the first substantially linear responseof the first stack portion 710. The second substantially linear responsecorresponds to the applied magnetic field over a second magnetic fieldstrength range.

In embodiments, the first substantially linear response of the firststack portion 710 results in the MR element 700 having a firstsensitivity level (i.e., a first rate of change in resistance) tochanges in magnetic field strength in response to the applied magneticfield being within the first magnetic field strength range.Additionally, in embodiments, the second substantially linear responseof the second stack portion 730 results in the MR element 700 having asecond sensitivity level (i.e., a second rate of change in resistance)to changes in magnetic field strength in response to the appliedmagnetic field being within the second magnetic field strength range. Inembodiments, the first magnetic field strength range (e.g., in Oersteds)overlaps with one or more portions of the second magnetic field strengthrange. Additionally, in embodiments, at least one of the first or secondmagnetic field strength ranges includes one or more sub-ranges (e.g.,603 b, 603 c, 603 d, 603 e, shown in FIG. 6), and the first and/orsecond substantially linear responses associated with the first andsecond magnetic field strength ranges includes corresponding sub-regions(e.g., 601 b, 601 c, 601 d, 601 e, shown in FIG. 6). In embodiments, thefirst linear range of the first stack portion includes sub-ranges 603A,603B, and 603C; and the second linear range of the second stack portionincludes sub-ranges 603A, 603B, 603C, 603D, and 603E. In this example,the linear ranges overlap at 603A, 603B and 603C proving those regionswith double sensitivity. In sub-ranges 603D and 603E, where there is nooverlap of the linear ranges of the stack portions, there may be normal(i.e. not double) sensitivity.

The first and second stack portions 710, 730 each have at least onecharacteristic (e.g., construction and/or dimensions) selected to resultin the first and second stack portions 710, 730 having the first andsecond substantially linear regions, respectively.

For example, one or more parameters associated with the construction ofthe first and second stack portions 710, 730 may comprise the at leastone characteristic selected to result in the first and second stackportions 710, 730 having the first and second substantially linearranges. Illustrative construction parameters include materials, layerthickness, and an ordering of one or more of the layers (e.g.,antiferromagnetic layers, pinned layers and/or non-magnetic layers) ofthe first and second stack portions 710, 730. The constructionparameters may also include a number of layers in the first and secondstack portions 710, 730.

In the illustrated embodiment, each of the layers in the first andsecond stack portions 710, 730 is shown as including one or morematerials. In embodiments, materials of one or more of the layers in thefirst stack portion 710 are selected to result in the first stackportion having the first substantially linear response. Additionally, inembodiments, materials of one or more of the layers in the second stackportion 730 are selected to result in the second stack portion havingthe second substantially linear response. For example, the material(s)of spacer layer 713 in the first stack portion 710 (here, Ruthenium(Ru)) and/or the material(s) of spacer layer 715 in the first stackportion 710 (here, Copper (Cu)) may be selected to result in the firststack portion 710 having the first substantially linear range.Additionally, the material(s) of spacer layer 732 in the second stackportion 730 (here, Cu) and/or the material(s) of spacer layer 734 in thesecond stack portion 730 (here, Ru) may be selected to result in thesecond stack portion 730 having the second substantially linear responserange. A spacer layer comprising Ru, for example, may provide forantiferromagnetic coupling or ferromagnetic coupling between surroundinglayers, which may provide for the first and/or second substantiallylinear ranges, as discussed further below.

It is understood that the material(s) of layers other than spacer layers713, 715 in the first stack portion 710 and spacer layers 732, 734 inthe second stack portion 730 may be selected to result in the first andsecond stack portions 710, 730 having the first and second substantiallylinear responses.

In the illustrated embodiment, each of the layers in the first andsecond stack portions 710 is also shown having a respective thickness.In embodiments, the thickness of at least one of the layers of the firststack portion 710 is selected to result in the first stack portionhaving the first substantially linear range. Additionally, inembodiments, the thickness of at least one of the layers of the secondstack portion 730 is selected to result in the second stack portionhaving the second substantially linear range. For example, spacer layer713 in the first stack portion 710 may have a first selected thickness(here, about 3.3 nm) to result in the first stack portion 710 having thefirst substantially linear range. Additionally, spacer layer 734 in thesecond stack portion 730 may have a second selected thickness that isdifferent than the first selected thickness to result in the secondstack portion 730 having the second substantially linear range that isdifferent than the first substantially linear range. In the exampleembodiment shown, spacer layer 734 has a thickness selected to be in oneof four example ranges, e.g., about 1.6 nanometers (nm) to about 1.8 nm,about 2.2 nm to about 2.4 nm, about 2.9 nm to about 3.1 nm, or about 3.5nm to about 3.7 nm.

In embodiments, the example ranges are determined by measuring atransfer curve associated with the MR element at different thicknesses(e.g., Ru thicknesses) of the spacer layer 734, and selecting athickness (or thicknesses) T1 of the spacer layer 734 to achieve aparticular substantially linear range. (e.g., a first and/or a secondsubstantially linear range). A spacer layer 734 having a thickness T1 ina first one of the thickness ranges (e.g., about 1.6 nm to about 1.8 nm)may, for example, have a different slope (sensitivity) parallel toresponse axis 699 than a spacer layer 734 having a thickness T1 in asecond one of the thickness ranges (e.g., about 2.2 nm to about 2.4 nm).

It is understood that thicknesses of layers other than spacer layer 713in the first stack portion 710 and spacer layer 734 in the second stackportion 730 may be selected to result in the first and second stackportions 710, 730 having the first and second substantially linearranges. It is also understood that the thicknesses of certain layers inthe first and second stack portions 710, 730 may be selected to providea desired amount and/or type of magnetic coupling between adjacentlayers in the first and second stack portions 710, 730. For example, thethickness of the spacer layer 713 in the first stack portion 710 may beselected to provide a desired amount of magnetic coupling between pinnedlayer 712 and free layer structure 714 in the first stack portion 710.Additionally, the thickness of the spacer layer 713 may be selected toprovide a desired type of magnetic coupling between the pinned layer 712and the free layer structure 714, i.e., ferromagnetic coupling orantiferromagnetic coupling, or between ferromagnetic andantiferromagnetic coupling.

Here, the coupling is shown to be ferromagnetic coupling, but, byselection of the thickness of the spacer layer 713, the coupling can beantiferromagnetic or between ferromagnetic and antiferromagneticcoupling. In other words, in the absence of an applied magnetic field itis possible for a magnetization direction of the free layers 714 a, 714b in the free layer structure 714 to be rotated either as shown (out ofthe page) or into the page, depending upon a selected thickness of thespacer layer 713. Additionally, by selection of the thicknesses of thespacer layers 732, 734, the coupling between layers adjacent to thespacer layers 732, 734 can be antiferromagnetic or ferromagnetic.

As another example, spacer layer 716 b in the first stack portion 710may have a first thickness (e.g., 0.85 nm) selected to provide a firstmagnetic coupling between surrounding layers (e.g., layers 716 a, 716 c)having a first coupling strength, and spacer layer 713 may have a secondthickness (e.g., 3.3 nm) selected to provide a second magnetic couplingbetween surrounding layers (e.g., layers 712, 714) having a secondcoupling strength that is different than (e.g., less than) the firstcoupling strength. Ru may, for example, be well suited for the spacerlayer 716 b and the spacer layer 713 since it allows antiferromagneticcoupling or ferromagnetic coupling between surrounding layers accordingto the Ru thickness. In other words, the materials and thicknesses oflayers in the first and second stack portions 710, 730 may be selectedto achieve a particular magnetic coupling (or coupling strength) betweensurrounding layers.

In embodiments, the first and second substantially linear ranges arebased, at least in part, upon the magnetic couplings occurring in thefirst and second stack portions 710, 730. In embodiments, the magneticcouplings are the main (or a main) factor determining the first andsecond substantially linear responses. Additionally, in embodiments, anannealing process used to manufacture the MR element 700 may affect themagnetic couplings, especially an angle at which the coupling occurs.

In the illustrated embodiment, the first plurality of layers in thefirst stack portion 710 and the second plurality of layers in the secondstack portion 730 are additionally shown arranged in a particularordering. In embodiments, an ordering of the first plurality of layersin the first stack portion 710 corresponds to the at least onecharacteristic selected to result in the first stack portion 710 havingthe first substantially linear range. Additionally, in embodiments anordering of the second plurality of layers in the second stack portion730 corresponds to the at least one selected to result in the secondstack portion 730 having the second substantially linear range. Forexample, due to the presence of the spacer layer 716 b between the firstand second pinned layers 716 a, 716 c in the pinned layer structure 716of first stack portion 710, the first pinned layer 716 a tends to coupleantiferromagnetically with the second pinned layer 716 c. As a result,the first pinned layer 716 a has a magnetization direction that pointsin a direction that is different than a magnetization direction in whicha magnetic field of the second pinned layer 716 b points. In otherwords, an ordering of the spacer layer 716 b and the first and secondpinned layers 716 a, 716 c may affect a type of coupling (e.g.,antiferromagnetic or ferromagnetic) which may occur between the firstand second pinned layers 716 a, 716 c, and the coupling may result inthe first stack portion 710 having the first substantially linear range.

In general, it has been found that the arrangement and orientation ofthe ferromagnetic and non-ferromagnetic layers of the MR element 700 canaffect the way the MR element 700 responds to the applied magneticfield. Additionally, different orientations of the ferromagnetic andnon-ferromagnetic layers of the MR element 700 can produce differenttypes of MR elements. In one embodiment, the MR element 700 is one of agiant magnetoresistance (GMR) element, a magnetic tunnel junction (MTJ)element and a tunneling magnetoresistance (TMR) element.

In the illustrated embodiment, the first plurality of layers in thefirst stack portion 710 and the second plurality of layers in the secondstack portion 730 are also shown including a particular number of layers(here, nine layers). In embodiments, the number of layers provided inthe first plurality of layers corresponds to the at least onecharacteristic selected to result in the first stack portion having thefirst substantially linear range. Additionally, in embodiments thenumber of layers provided in the second plurality of layers correspondsto the at least one characteristic selected to result in the secondstack portion having the second substantially linear range.

In some embodiments, the first plurality of layers includes a samenumber of layers as the second plurality of layers, as shown in FIG. 7,for example. In other embodiments, the first plurality of layersincludes a different number of layers than the second plurality oflayers. An example MR element according to the disclosure comprisingfirst and second stack portions having respective first and secondpluralities of layers with a different number of layers is shown anddescribed below in connection with FIG. 12, for example.

In general, it has been found that the materials, layer thicknesses, anordering and a number of layers in the first and second stack portions710, 730 can affect the manner in which the first and second stackportions 710, 730 of the MR element 700 respond to an applied magneticfield.

For example, in one embodiment the materials of spacer layer 713 infirst stack portion 710 are selected to affect the manner in which theMR element 700 responds to the applied magnetic field, and provide forthe various sub-regions 601 b, 601 c, 601 d, 601 e of the secondsubstantially linear range shown in FIG. 6, for example. In theillustrated embodiment, for example, Ru was selected as a material forspacer layer 713 since with Ru it is possible to establish a relativelygood coupling between free layer 714 and bias portions (e.g., layer 711and/or layer 712) of the first stack portion 710. With materials otherthan Ru (e.g., Ta) selected for spacer layer 713, similar couplings maybe achieved, but for different thicknesses of the layer 713. Inembodiments, the thickness of the Ru in spacer layer 713 may also affectthe manner in which the MR element 700 responds to the applied magneticfield. For example, in some embodiments the coupling through the Ru inspacer layer 713 oscillates between ferromagnetic (F) andantiferromagnetic (AF) and for some thicknesses of Ru the coupling isclose to zero. The type of the coupling (AF vs F) may not determine thelinear range of a linear region (e.g., linear region 601 a), but astrength of the coupling may determine (or at least impact) the linearrange. As one example, if the thickness of the Ru in spacer layer 713 infirst stack portion 710 provides for a coupling strength that is similarto a coupling strength obtained through spacer layer 734 in second stackportion 730, the first and second stack portions 710, 730 may behave ina same or similar way and the desired piecewise response may not beprovided. However, if one of spacer layers 713, 734 has a thickness(and/or material) that provides for a coupling amplitude that is lowerthan the other, the piecewise response may appear. In one embodiment,the lower the coupling strength, the narrower the magnetic fieldstrength range 603 a of linear region 601 a, for example. In embodimentsin which there is substantially no coupling, there is a steep transition(i.e., a steep slope or increased sensitivity) in linear region 601 a.

While MR element 700 is shown as having particular layers formed fromparticular materials, it is understood that the MR element 700 isillustrative of one example configuration of an MR element according tothe disclosure. Other layers and materials can, for example, be providedin the MR element 700. Additionally, one or more of the above-describedlayers of MR element 700 may include a plurality of layers (orsub-layers) in some embodiments. Additionally, in some embodiments, oneor more other layers (not shown) can be interposed between the layers ofMR element 700.

In embodiments, the MR element 700 is provided in a magnetic fieldsensor (e.g., 1500, shown in FIG. 15, as discussed below) or anothersensing circuit. As discussed above, a magnetic field sensor is used todescribe a circuit that uses a magnetic field sensing element, generallyin combination with other circuits. In embodiments, the MR element 700and the other circuits of the magnetic field sensor can be integratedupon a common substrate (here, substrate 701).

Additional aspects of MR elements according to the disclosure aredescribed below.

Referring now to FIG. 8, in which like elements of FIG. 7 are providedhaving like reference designations, a second example MR element 800according to the disclosure includes a first stack portion 810 and asecond stack portion 830. The first stack portion 810 has first andsecond opposing surfaces, with first surface of the first stack portion810 disposed over seed layer 702 and the seed layer 702 disposed betweenthe first stack portion 810 and the substrate 701 on which the MRelement 800 is deposited on. Additionally, the second stack portion 830has first and second opposing surfaces, with the first surface of thesecond stack portion 830 disposed over pinning layer 720 and the pinninglayer 720 disposed between the first stack portion 810 and the secondstack portion 830. Cap layer 704 is disposed over the second surface ofthe second stack portion 830.

The first stack portion 810 includes a first plurality of layers (here,9 layers). The first plurality of layers includes pinning layer 711,pinned layer 712 and a spacer layer 813. The first stack portion 810also includes free layer structure 714, spacer layer 715 and pinnedlayer structure 716. The first free layer structure 714 includes firstfree layer 714 a and second free layer 714 b. Additionally, the pinnedlayer structure 716 includes first pinned layer 716 a, second pinnedlayer 716 c and spacer layer 716 b.

The pinning layer 711 is disposed over the seed layer 702 and the pinnedlayer 712 is disposed over the pinning layer 711. Additionally, spacerlayer 813 is disposed over the pinned layer 712 and free layer structure714 is disposed over the spacer layer 813. Further, spacer layer 715 isdisposed over the free layer structure 714 and pinned layer structure716 is disposed over the spacer layer 715. Spacer layer 813, which maybe similar to spacer layer 713 of MR element 700 shown in FIG. 7 buthaving a thickness that is different than a thickness of the spacerlayer 713, may be a nonmagnetic spacer layer.

The second stack portion 830 includes a second plurality of layers(here, 9 layers), i.e., a same number of layers as the first pluralityof layers of first stack portion 810 in the illustrated embodiment. Thesecond plurality of layers includes pinned layer structure 731, spacerlayer 732 and free layer structure 733. The second plurality of layersalso includes spacer layer 834 and pinned layer 735. The pinned layerstructure 731 includes first pinned layer 731 a, second pinned layer 731c and spacer layer 731 b. Additionally, free layer structure 733includes first free layer 733 a and second free layer 733 b.

The pinned layer structure 731 is disposed over the pinning layer 720and the spacer layer 732 is disposed over the pinned layer structure731. Additionally, the free layer structure 733 is disposed over thespacer layer 732 and the spacer layer 834 is disposed over the freelayer structure 733. Further, the pinned layer 735 is disposed over thespacer layer 834 and the pinning layer 736 is disposed over the pinnedlayer 735. Spacer layer 834, which may be similar to spacer layer 734 ofMR element 700 shown in FIG. 7 but having a thickness that is differentthan a thickness of the spacer layer 734, may be a nonmagnetic spacerlayer comprising one or more nonmagnetic materials (e.g., Ru).

Similar to first stack portion 710 in MR element 700 of FIG. 7, thefirst stack portion 810 in MR element 800 has a first substantiallylinear response corresponding to an applied magnetic field over a firstrange of magnetic field strengths (i.e., a first magnetic field strengthrange). Additionally, similar to second stack portion 730 in MR element700 of FIG. 7, the second stack portion 830 in MR element 800 has asecond substantially linear response that is different than the firstsubstantially linear response, the second substantially linear responsecorresponding to the applied magnetic field over a second range ofmagnetic field strengths (i.e., a second magnetic field strength range).In embodiments, the first magnetic field strength range overlaps withone or more portions of the second magnetic field strength range. The MRelement 800 has a maximum response axis to the applied magnetic fieldwhich is parallel to the substrate surface (e.g., a first surface of thesubstrate 801) over which the MR element 800 is disposed, as indicatedby arrow 799.

The first stack portion 810 has at least one characteristic selected toresult in the first stack portion 810 having the first substantiallylinear response. Additionally, the second stack portion 830 has at leastone characteristic selected to result in the second stack portion 830having the second substantially linear response. The at least onecharacteristic may include: materials, layer thickness and an orderingof one or more of the layers in the first and second stack portions 810,830. Additionally, the at least one characteristic may also include anumber of layers in the first and second stack portions 810, 830.

In the illustrated embodiment, the thickness of spacer layer 813 infirst stack portion 810 may, for example, correspond to the at least onecharacteristic selected to result in the first stack portion 810 havingthe first substantially linear response. For example, the spacer layer813 may have a thickness selected (here, about 1.3 nm) to result in thefirst stack portion 810 having a first predetermined bias (e.g., a“strong” bias) which, in turn, may result in the first stack portion 810having the first substantially linear response.

Additionally, in the illustrated embodiment, the thickness T2 of spacerlayer 834 in second stack portion 830 may correspond to the at least onecharacteristic selected to result in the second stack portion 830 havingthe second substantially linear response. For example, the spacer layer834 may have a thickness selected (e.g., about 1.7 nm) to result in thesecond stack portion 830 having a second predetermined bias (e.g., a“very weak” bias) which, in turn, may result in the second stack portion830 having the second substantially linear response.

In embodiments, the first stack portion 810 of MR element 800 has afirst substantially linear response that is different than the firstsubstantially linear response of first stack portion 710 of MR element700, e.g., due to the at least one characteristic selected to result inthe first stack portion 810 having the first substantially linearresponse. For example, in the illustrated embodiment, spacer layer 813of first stack portion 810 having a different thickness than spacerlayer 713 of first stack portion 710 may result in the first stackportion 810 of MR element 800 having a first substantially linearresponse that is different than the first substantially linear responseof first stack portion 710 of MR element 700.

Additionally, the first stack portion 810 having a first substantiallylinear response that is different than the first substantially linearresponse of first stack portion 710 of MR element 700 may, for example,result in the first stack portion 810 having a first sensitivity level(i.e., rate of change in resistance) to changes in magnetic fieldstrengths over a first range of magnetic field strengths that isdifferent than a first sensitivity level of the first stack portion 710over a similar range of magnetic fields strengths as the first range ofmagnetic field strengths. In embodiments, the first stack portion 810may have a first sensitivity level that is substantially the same as afirst sensitivity level of the first stack portion 710, but over adifferent range of magnetic field strengths, for example. As discussedabove, in embodiments, the first range of magnetic field strengths maybe based upon the at least one characteristic selected to result in thefirst stack portion (e.g., 810) having the first substantially linearresponse.

Additionally, in embodiments, the second stack portion 830 of MR element800 has a second substantially linear response that is different thanthe second substantially linear response of second stack portion 730 ofMR element 700 due to the at least one characteristic selected to resultin the second stack portion 830 having the second substantially linearresponse. For example, in the illustrated embodiment, spacer layer 834of second stack portion 830 of MR element 800 having a thickness T2 thatis different from a thickness T1 of spacer layer 734 of second stackportion 730 of MR element 700 may result in the second stack portion 830of MR element 800 having a second substantially linear response that isdifferent than the second substantially linear response of second stackportion 730 of MR element 700.

In one embodiment, first stack portion 710 of MR element 700 has a firstcoupling strength and the first stack portion 810 of MR element 800 hasa second coupling strength that is different from (e.g., larger than)the first coupling strength. The foregoing may be due to the first stackportion 810 of MR element 800 having one or more characteristics thatare different from one or more characteristics of the first stackportion 710 of MR element 700. For example, as illustrated, spacer layer813 of first stack portion 810 has a thickness that is different fromspacer layer 713 of first stack portion 710. In embodiments, such mayresult in the second coupling strength of the first stack portion 810 ofMR element 800 being larger than the first coupling strength of thefirst stack portion 710 of MR element 700. The larger coupling strengthof the first stack portion 810 may, for example, result in the MRelement 800 having a plurality of substantially linear sub-regions thatare different from a like plurality of substantially linear regions orsub-regions of MR element 700. For example, with respect to the curves602, 604 shown in FIG. 6, the MR element 800 may have second and thirdsubstantially linear regions (e.g., 601 b, 601 c) with magnetic fieldstrength sub-ranges (e.g., 603 b, 603 d) that are different from (e.g.,larger than) magnetic field strength sub-ranges associated with secondand third substantially linear regions of the MR element 700.Additionally, the MR element 800 may have fourth and fifth substantiallylinear regions (e.g., 601 d, 601 e) with magnetic field strengthsub-ranges (e.g., 603 d, 603 e) that are different from (e.g., largerthan) magnetic field strength sub-ranges associated with fourth andfifth substantially linear regions of the MR element 700. Further, theMR element 800 may have a first sensitivity level over a first magneticfield strength sub-range (e.g., 603 a) that is different from (e.g.,larger than) a first sensitivity level over the MR element 700 over acorresponding first magnetic field strength sub-range.

In one embodiment, the second coupling strength of the first stackportion 810 of MR element 800 corresponds to a coupling strength ofabout 200 Oe, which may be representative of a very strong couplingstrength. One example results of the second coupling strength of firststack portion 810 of MR element 800 being so strong is that manythicknesses of spacer layer 834 in second stack portion 830 of MRelement 800, especially thicknesses of above about 2.3 nm in someembodiments, may provide for the MR element 800 having a substantiallypiecewise linear response. MR element 800 may, for example, have arelatively narrow first substantially linear region (e.g., 601 a) and arelatively high first sensitivity level over a first magnetic fieldstrength sub-range (e.g., 603 a) when spacer layer 834 has a thicknessof about 2.4 nm, 3.1 nm, 3.6 nm and 4.3 nm.

The second stack portion 830 having a second substantially linearresponse that is different than the second substantially linear responseof first stack portion 730 of MR element 700 may also result in thesecond stack portion 830 having a second sensitivity level (i.e., rateof change in resistance) to changes in magnetic field strengths over asecond range of magnetic field strengths that is different than a secondsensitivity level of the second stack portion 730 over a similar rangeof magnetic fields strengths as the first range of magnetic fieldstrengths. In embodiments, the second stack portion 830 may have asecond sensitivity level that is substantially the same as a secondsensitivity level of the second stack portion 730, but over a differentrange of magnetic field strengths, for example. As discussed above, inembodiments, the second range of magnetic field strengths may be basedupon the at least one characteristic selected to result in the secondstack portion (e.g., 830) having the second substantially linearresponse.

In embodiments, the MR element 800 is provided in a magnetic fieldsensor (e.g., 1500, shown in FIG. 15, as discussed below), and the MRelement 800 is configured to generate the first and second substantiallylinear responses discussed above. Additionally, in embodiments, thefirst and second substantially linear responses have substantially zerooffset with respect to an expected response of the MR element 800 at anapplied magnetic field strength of about zero Oersteds (i.e., the MRelement 800 is annealed for a substantially zero offset). The foregoingmay, for example, result in the MR element 800 having substantially nooffset, for example, when experiencing an applied magnetic field havinga magnetic field strength of about zero Oersteds. Additionally, theforegoing may result in the linear range of the MR element 800 beingsubstantially evenly distributed about zero Oersteds, as furtherdiscussed below.

Referring to FIG. 9, in which like elements of FIG. 7 are shown havinglike reference designations, a third example MR element 900 includes afirst stack portion 910 and a second stack portion 930. The first stackportion 910 has first and second opposing surfaces, with the firstsurface of the first stack portion 910 disposed over seed layer 702 andthe seed layer 702 disposed between the first stack portion 910 and thesubstrate 701 on which the MR element 900 is deposited upon.Additionally, the second stack portion 930 has first and second opposingsurfaces, with the first surface of the second stack portion 930disposed over pinning layer 720 and the pinning layer 720 disposedbetween the first stack portion 910 and the second stack portion 930.Cap layer 704 is disposed over the second surface of the second stackportion 930.

The first stack portion 910 includes a first plurality of layers (here,6 layers), i.e., fewer layers than first stack portion 710 of MR element700 shown in FIG. 7 and first stack portion 810 of MR element 800 shownin FIG. 8. The first plurality of layers includes free layer structure714, spacer layer 715 and pinned layer structure 716. The free layerstructure 714 includes first free layer 714 a and second free layer 714b. Additionally, the pinned layer structure 716 includes first pinnedlayer 716 a, second pinned layer 716 c and spacer layer 716 b.

The free layer structure 714 is disposed over the seed layer 702 and thespacer layer 715 is disposed over the free layer structure 714.Additionally, the pinned layer structure 716 is disposed over the spacerlayer 715.

The second stack portion 930 includes a second plurality of layers(here, 6 layers), i.e., a same number of layers as the first pluralityof layers of first stack portion 910 in the illustrated embodiment. Thesecond plurality of layers includes pinned layer structure 731, spacerlayer 732 and free layer structure 733. The pinned layer structure 731includes first pinned layer 731 a, second pinned layer 731 c and spacerlayer 731 b. Additionally, the free layer structure 733 includes firstfree layer portion 733 a and second free layer portion 733 b.

The pinned layer structure 731 is disposed over the pinning layer 720and the spacer layer 732 is disposed over the pinned layer structure731. Additionally, the free layer structure 733 is disposed over thespacer layer 732.

Similar to first stack portion 810 in MR element 800 of FIG. 8, thefirst stack portion 910 in MR element 900 has a first substantiallylinear response corresponding to an applied magnetic field over a firstmagnetic field strength range. Additionally, similar to second stackportion 830 in MR element 800 of FIG. 8, the second stack portion 1130in MR element 900 has a second substantially linear response that isdifferent than the first substantially linear response, the secondsubstantially linear response corresponding to the applied magneticfield over a second magnetic field strength range. The MR element 900has a maximum response axis to magnetic fields (e.g., the appliedmagnetic field) which is parallel to the substrate surface (e.g., afirst surface of the substrate 701) over which the MR element 900 isdisposed, as indicated by arrow 899.

The first stack portion 910 has at least one characteristic selected toresult in the first stack portion 910 having the first substantiallylinear response. Additionally, the second stack portion 930 in MRelement 900 has at least one characteristic selected to result in thesecond stack portion 930 having the second substantially linearresponse. As discussed in figures above, the at least one characteristicmay include: materials, layer thickness and an ordering of one or moreof the layers in the first and second stack portions 910, 930.Additionally, the at least one characteristic may also include a numberof layers in the first and second stack portions 910, 930.

In the illustrated embodiment, materials and/or layer thicknesses of thefirst and second free layers 714 a, 714 b of free layer structure 714 inthe first stack portion 910 may, for example, correspond to the at leastone characteristic selected to result in the first stack portion 910having the first substantially linear response. For example, the firstand second free layer layers 714 a, 714 b may have materials and/orlayer thickness selected to result in the free layer structure 714 beinga substantially unbiased free layer which, in turn, may result in thefirst stack portion 910 having the first substantially linear response.

Additionally, in embodiments, the number of layers in the first andsecond stack portions 910, 930 may be selected alone, or in combinationwith materials, layer thickness and an ordering of one or more of thelayers in the first and second stack portions 910, 930 to result in thefirst and second substantially linear responses. In other words, the atleast one characteristic selected to result in the first and secondsubstantially linear responses may include the number of layers in thefirst and second stack portions 910, 930 and materials, layer thicknessand an ordering of one or more of the layers in the first and secondstack portions 910, 930.

In some embodiments, the first stack portion 910 has a same or similarfirst substantially linear response as the first substantially linearresponse of the first stack portion 810 in MR element 800 of FIG. 8despite comprising a different number of layers than the first stackportion 810. Additionally, in some embodiments, the second stack portion930 has a same or similar second substantially linear response as thesecond substantially linear response of the second stack portion 830 inMR element 800 of FIG. 8 despite comprising a different number of layersthan the second stack portion 830. For example, materials, layerthickness and/or an ordering of one or more of the layers in the firststack portion 910 may be selected to result in the first stack portion910 having a same or similar substantially linear response as the firstsubstantially linear response of the first stack portion 810. In otherwords, materials, layer thickness and/or an ordering of one or more ofthe layers in the first stack portion 910 may comprise the at least onecharacteristic selected to result in the first stack portion 910 havingthe first substantially linear response.

It is understood that the first stack portion 910 may also have a firstsubstantially linear response that is different from the firstsubstantially linear response of the first stack portion 810.Additionally, it is understood that the first stack portion 910 having afirst substantially linear response that is different than the firstsubstantially linear response of first stack portion 810 may, forexample, result in the first stack portion 910 having a firstsensitivity level (i.e., rate of change in resistance) to changes inmagnetic field strengths over a first range of magnetic field strengthsthat is different than a first sensitivity level of the first stackportion 810 over a similar range of magnetic fields strengths as thefirst range of magnetic field strengths.

Referring now to FIG. 10, a plot 1000 shows curves 1002, 1004representative of first example response characteristics of the MRelement 900 of FIG. 9 as it is exposed to magnetic fields of varyingstrengths in a transverse direction relative to the maximum responseaxis 899 of the MR element 900. The plot 1000 has a horizontal axis witha scale in magnetic field strength units (here, Oersteds (Oe)) and avertical axis with a scale in resistance units (here, Ohms). Similar toplots 300 and 500 shown in FIGS. 3 and 5, respectively, positivemagnetic field strength units (e.g., +X) in plot 1000 may correspond toa magnetic field experienced by the MR element 900 in a first direction,such as in response to a first direction of motion (e.g., rotation) byan object (e.g., ring magnet 1510, shown in FIG. 15). Additionally,negative magnetic field strength units (e.g., −X) in plot 1000 maycorrespond to a magnetic field experienced by the MR element 900 in asecond direction that is opposite from the first direction, such as inresponse to a second direction of motion by the object that is oppositefrom the first direction of motion of the object.

Curve 1002 corresponds to a response characteristic of the MR element900 as it is exposed to a magnetic field that sweeps from a positivemagnetic field strength value (e.g., 600 Oe) to a negative magneticfield strength value (e.g., −500 Oe), e.g., from the first direction ofmotion to the second direction of motion. Additionally, curve 1004corresponds to a response characteristic of the MR element 900 as itexposed to a magnetic field that sweeps a negative magnetic fieldstrength value (e.g., −500 Oe) to a positive magnetic field strengthvalue (e.g., 600 Oe), e.g., from the second direction of motion to thefirst direction of motion.

Curves 1002, 1004 have a first substantially linear region 1001 a and asecond substantially linear region (here, a second substantially linearregion including substantially linear sub-regions 1001 b, 1001 c).Curves 1002, 1004 also have first and second saturation regions 1001 d,1001 e. As is illustrated, sub-region 1001 b of the second substantiallylinear region is separated from sub-region 1001 c of the secondsubstantially linear region by the first substantially linear region1001 a.

A first end of the first substantially linear region 1001 a occurs at apoint at which the first substantially linear region 1001 a has a slopethat deviates from an average slope of a sub-region of the secondsubstantially linear region with which it is associated, for example,sub-region 1001 b, by a predetermined amount (e.g., about five percent).Additionally, a second opposing end of the first substantially linearregion 1001 a occurs at a point at which the first substantially linearregion 1001 a has a slope that deviates from the average slope of asub-region of the second substantially linear region with which it isassociated, for example, sub-region 1001 c, by about predeterminedamount (e.g., about five percent). The first and second substantiallylinear regions (i.e., regions 1001 a, 1001 b, 1001 c) correspond to anoperational range of the MR element 900 in the illustrated embodiment inwhich the MR element 900 has a resistance that is substantiallyresponsive to changes in magnetic field strength of the applied magneticfield.

In embodiments, the first substantially linear region 1001 a correspondsto the first substantially linear response of the first stack portion910 of MR element 900 discussed above in connection with FIG. 9, withthe first substantially linear response corresponding to an appliedmagnetic field over a first magnetic field strength range 1003 a (here,between about −5 Oe and about 5 Oe, i.e., a limited range of magneticfield strengths).

Additionally, in embodiments, the second substantially linear region(i.e., sub-regions 1001 b, 1001 c) corresponds to the secondsubstantially linear response of the second stack portion 930 of MRelement 900 discussed above in connection with FIG. 9, with the secondsubstantially linear response corresponding to the applied magneticfield over a second magnetic field strength range (here, a secondmagnetic field strength range including sub-ranges 1003 b, 1003 c). Inthe illustrated embodiment, sub-range 1003 b comprises magnetic fieldstrengths between about −5 Oe and about −100 Oe). Additionally, in theillustrated embodiment, sub-range 1003 c comprises magnetic fieldstrengths between about 5 Oe and about 80 Oe).

As discussed above, the second substantially linear response of secondstack portion 930 is different than the first substantially linearresponse of first stack portion 910. In the illustrated embodiment, thesecond substantially linear response occurs over a second range ofmagnetic field strengths (here, sub-ranges 1003 b, 1003 c) that isdifferent than the first range of magnetic field strengths 1003 a. Inembodiments, the MR element 900 has a respective substantially linearresponse in each of the sub-regions 1001 b, 1001 c of the secondsubstantially linear region associated with the second substantiallylinear response, with the substantially linear responses of the MRelement 900 in sub-regions 1001 b, 1001 c (e.g., fourth and fifthsubstantially linear responses) comprising the second substantiallylinear response of the second substantially linear region.

The first substantially linear response of the first stack portion 910results in the MR element 900 having a first sensitivity level (i.e., afirst rate of change in resistance) to changes in magnetic fieldstrength when the applied magnetic field is within the first range ofmagnetic field strengths 1003 a. The first sensitivity level may bedetermined, for example, by observing an average slope of curves 1002,1004 in first substantially linear region 1001 a. Additionally, thesecond substantially linear response of the second stack portion 930results in the magnetoresistance element having a second sensitivitylevel (i.e., a second rate of change in resistance) to changes inmagnetic field strength when the applied magnetic field is within thesecond range of magnetic field strengths (here, sub-ranges 1003 b, 1003c). The second sensitivity level may be determined, for example, byobserving an average slope of curves 1002, 1004 in the secondsubstantially linear region (i.e., sub-regions 1001 b, 1001 c of thesecond substantially linear region).

The second sensitivity level is reduced in comparison to the firstsensitivity level in the illustrated embodiment. It follows that the MRelement 900 has a higher sensitivity to changes in magnetic fieldstrength in the first substantially linear region 1001 a (i.e., over asmall or limited range a magnetic fields) than it does to changes inmagnetic field strength in the second substantially linear region (i.e.,sub-regions 1001 b, 1001 c, which comprise a more expansive range ofmagnetic fields than region 1001 a). The first sensitivity level of theMR element 900 in the illustrated embodiment (e.g., resulting in the MRelement 900 having a resistance that substantially varies at a magneticfield strength of about zero) may, for example, be given by rotation offree layer 714 or other layers of the first stack portion 910 of MRelement 900. Additionally, the first sensitivity level of the MR element900 may be due to the lack of a biasing part (e.g., layer 712, shown inFIG. 7) in the MR element 900. The illustrated first sensitivity levelof the MR element 900 may, for example, be desirable in embodiments inwhich an absolute field sensor is not needed, but it is desirable forthe MR element 900 (e.g., an output of the MR element 900) to switch ata certain threshold or range of magnetic field strengths. In otherembodiments, the first sensitivity level may have a reduced sensitivity(i.e., a reduced slope in region 1001 a) from that which is shown.Additionally, in other embodiments, the first sensitivity level may bereduced in comparison to the second sensitivity level.

In embodiments, MR element 900 has a respective sensitivity level tochanges in magnetic field strength in the applied magnetic field in eachof the sub-regions 1001 b, 1001 c of the second substantially linearregion, with the sensitivity levels of the MR element 900 in thesub-regions 1001 b, 1001 c (e.g., fourth and fifth sensitivity levels)comprising the second sensitivity level of the second substantiallylinear region.

Additionally, in embodiments, at least one characteristic (e.g., layerthicknesses of one or more layers) of the first and second stackportions 910, 930 may be selected to tune or alter one or more regionsof the curves 1002, 1004, similar to the at least one characteristicselected to provide the first and second substantially linear responsesof the first and second stack portions 710, 730 of MR element 700discussed above in connection with FIG. 7, for example.

As illustrated, unlike prior art MR element 400 of FIG. 4, for example,in which the first and second stack portions 410, 430 behaveantisymmetrically (i.e., substantially equal and opposite) to an appliedmagnetic field, resulting in the MR element 400 having a singlesubstantially linear response over a single substantially linear region401 a, as shown in plot 500, the first and second stack portions 910,930 of the MR element 900 have a first and second different, respectivesubstantially linear responses to the applied magnetic field. As aresult of the foregoing, the MR element 900 has a first substantiallylinear response over a first substantially linear region 1001 a and asecond substantially linear response that is different than the firstsubstantially linear response over a second substantially linear region(here, sub-regions 1001 b, 1001 c) that is different than the firstsubstantially linear region 1001 a. In embodiments, the first and secondsubstantially linear responses of MR element 900 are provided at leastin part from pinning layer 720, more particularly the crystal structurecoming from the PtMn growth of pinning layer 720. This is contrast tothe MR element 400 of FIG. 4 in which Ru spacer layers 413, 434 providefor the single substantially linear response of MR element 400 inembodiments, for example, due to the Ru spacer layers 413, 434stabilizing free layers 414, 433.

As also illustrated, MR element 900 has a reduced offset compared to theprior art MR element 400 and to the prior art MR element 200, asdepicted by curves 1002, 1004 which are less horizontally offset with anintersection of the vertical and horizontal axes of plot 1000, thancurves 502, 504 shown in plot 500 of FIG. 5 and curves 304, 304 shown inplot 300 of FIG. 3. As a result of the foregoing, the range of magneticfield strengths to which the MR element 900 is responsive also has areduced offset compared the prior art MR element 400 and to the priorart MR element 200.

In embodiments, the increased operational range of the MR element 900may also provide for increased offset drift toleration by the MR element900, such as that which may occur due to temperature, age and/or amisalignment or misplacement between the MR element and an object (i.e.,a magnetic field) sensed by the MR element 900, for example. Inparticular, due to the increased operational range of MR element 900(i.e., a greater range of magnetic fields that may be sensed by the MRelement 900), MR element 900 may be able to sense magnetic fields thatwould otherwise not be detected by conventional MR elements (e.g., MRelement 200), making offset drift may be more tolerable. In general, aMR element according to the disclosure having a first operational rangemay have an increased offset drift tolerance in comparison to aconventional MR element having a second operational range that is lessthan the first operational range. Remaining offset errors (if any) can,for example, be corrected in signal processing circuitry coupled anoutput (e.g., V_(OUT), shown in FIG. 14, as discussed below) of the MRelement.

In embodiments, the increased operational range of the MR element 900may further provide for improved immunity to common field interferenceby the MR element 900. In particular, as is known in the art, commonfield interference may add an offset to a magnetic field signal (i.e.,an applied magnetic field) to which an MR element (e.g., 900) mayexperience. The offset could cause the MR element to become saturated ifthe linear or operational range of the MR element is too small. Inembodiments, the increased linear or operational range of the MR element900 (and other MR elements according to the disclosure) substantiallyreduces (or ideally prevents) saturation of the MR element 900 whensubjected to common field interference (and the offset resulting fromcommon field interference).

Referring now to FIG. 11, a plot 1100 shows curves 1102, 1104representative of second example response characteristics (i.e.,transfer curves) of the MR element 900 of FIG. 9 as it is exposed tomagnetic fields of varying strengths in a direction substantiallyparallel to the maximum response axis 899 of the MR element 900. Theplot 1100 has a horizontal axis with a scale in magnetic field strengthunits (here, Oersteds (Oe)) and a vertical axis with a scale inresistance units (here, Ohms).

Curve 1102 corresponds to a response characteristic of the MR element900 as it is exposed to a magnetic field that sweeps from a positivemagnetic field strength value (e.g., 200 Oe) to a negative valuemagnetic field strength value (e.g., −200 Oe). Additionally, curve 1104corresponds to a response characteristic of the MR element 900 as itexposed to a magnetic field that sweeps from the negative magnetic fieldstrength value (e.g., −200 Oe) to the positive magnetic field strengthvalue (e.g., 200 Oe).

As illustrated, the curves 1102, 1104 have first and secondsubstantially linear regions 1101 a, 1101 b in which the MR element 900characterized by curves 1102, 1104 has a relatively low resistance whenexposed to lower strength magnetic fields. Additionally, the curves1102, 1104 have first and second saturation regions 1101 c, 1101 d inwhich the MR element 900 has a relatively high resistance when exposedto a higher strength magnetic fields. In substantially linear region1101 a, the MR element 900 characterized by curves 1102, 1104 has afirst substantially linear response corresponding to the appliedmagnetic field greater than a first threshold, or within a firstmagnetic field strength range. Additionally, in substantially linearregion 1101 b, the MR element 900 has a second substantially linearresponse that is different than the first substantially linear response,the second substantially linear response corresponding to the appliedmagnetic field less than a second threshold, or within a second magneticfield strength range. In the saturation regions 1101 c, 1101 d, the MRelement 900 is substantially unresponsive to the applied magnetic field.

As also illustrated, the curves 1102, 1104 have respective peaks 1102 a,1104 a at about zero Oersteds. Additionally, curves 1102, 1104 aresubstantially centered around zero Oersteds, and the substantiallylinear ranges 1101 a, 1101 b of the MR element 900 are substantiallyuniform in magnitude of ranges of magnetic field strengths (−Oe to +Oe).In embodiments, such corresponds to the MR element characterized bycurves 1102, 1104 having a small (ideally, nonexistent) offset.

In embodiments, the peaks of curves associated with MR elementsaccording to the disclosure (similar to peaks 1102 a, 1104 a of curves1102, 1104) generally appear at an amplitude corresponding to a biasfield, with the bias field determined by a thickness of one or morelayers (e.g., Ru spacers 713 and 734) of the MR element. However, the MRelement 900 to which curves 1102, 1104 shown in FIG. 11 are associatedwith, for example, does not have Ru spacers (e.g., Ru spacers 713 and734) and a biasing part. One example result of the foregoing is peaks1102 a, 1104 a of curves 1102, 1104 are substantially overlapping atabout zero Oersteds.

Referring to FIG. 12, in which like elements of FIGS. 8 and 11 are shownhaving like reference designations, a fourth example MR element 1200includes a first stack portion 910 and a second stack portion 1230. Thefirst stack portion 910 has first and second opposing surfaces, with thefirst surface of the first stack portion 910 disposed over seed layer702 and the seed layer 702 disposed between the first stack portion 910and the substrate on which the MR element 1200 is deposited upon.Additionally, the second stack portion 1230 has first and secondopposing surfaces, with the first surface of the second stack portion1230 disposed over pinning layer 720 and the pinning layer 720 disposedbetween the first stack portion 910 and the second stack portion 930.Cap layer 704 is disposed over the second surface of the second stackportion 1230.

The first stack portion 910 (i.e., a same first stack portion as thefirst stack portion of MR element 900) includes a first plurality oflayers (here, 6 layers). Additionally, the second stack portion 1230includes a second plurality of layers (here, 9 layers), i.e., adifferent number of layers as the first plurality of layers.

The second plurality of layers of second stack portion 1230 includespinned layer structure 731, spacer layer 732 and free layer structure733. The second plurality of layers also includes a spacer layer 1234,pinned layer 735 and pinning layer 736. The pinned layer structure 731includes first pinned layer 731 a, second pinned layer 731 c and spacerlayer 731 b. Additionally, free layer structure 733 includes first freelayer 733 a and second free layer 733 b.

The pinned layer structure 731 is disposed over the pinning layer 720and the spacer layer 732 is disposed over the pinned layer structure731. Additionally, the free layer structure 733 is disposed over thespacer layer 732 and the spacer layer 1234 is disposed over the freelayer structure 733. Further, the pinned layer 735 is disposed over thespacer layer 1234 and the pinning layer 736 is disposed over the pinnedlayer 735. Spacer layer 1234, which may be similar to spacer layer 734of MR element 700 shown in FIG. 7 but having a thickness that isdifferent than a thickness of the spacer layer 734, may be a nonmagneticspacer layer comprising one or more nonmagnetic materials (e.g., Ru).

The first stack portion 910 in the MR element 1200 has a firstsubstantially linear response corresponding to an applied magnetic fieldover a first magnetic field strength range. Additionally, the secondstack portion 1230 in the MR element 1200 has a second substantiallylinear response that is different than the first substantially linearresponse, the second substantially linear response corresponding to theapplied magnetic field over a second magnetic field strength range. TheMR element 1200 has a maximum response axis to magnetic fields (e.g.,the applied magnetic field) which is parallel to the substrate surface(e.g., a first surface of the substrate 701) over which the MR element1200 is disposed, as indicated by arrow 1199.

The first stack portion 910 has at least one characteristic selected toresult in the first stack portion 910 having the first substantiallylinear response. Additionally, the second stack portion 1230 has atleast one characteristic selected to result in the second stack portion1230 having the second substantially linear response.

In the illustrated embodiment, the thickness of spacer layer 1234 insecond stack portion 1230 may, for example, correspond to the at leastone characteristic selected to result in the second stack portion 1230having the second substantially linear response. For example, the spacerlayer 1234 may have a thickness selected (here, about 4 nm) to result inthe second stack portion 1230 having an antiferromagnetic partial biaswhich, in turn, may result in the second stack portion 1230 having thesecond substantially linear response.

Referring to FIG. 13, in which like elements of FIG. 8 are shown havinglike reference designations, a fifth example MR element 1300 includes afirst stack portion 810, a second stack portion 1330 and a third stackportion 1350, i.e., an additional stack portion over the MR elementsdiscussed in figures above. The first stack portion 810 has first andsecond opposing surfaces, with the first surface of the first stackportion 810 disposed over the seed layer 702 and the seed layer 702disposed between the first stack portion 810 and the substrate 701 onwhich the MR element 1300 is deposited upon. Additionally, the secondstack portion 1330 has first and second opposing surfaces, with thefirst surface of the second stack portion 1330 disposed over pinninglayer 720 and the pinning layer 720 disposed between the first stackportion 810 and the second stack portion 1330. Further, the third stackportion 1350 has first and second opposing surfaces, with the firstsurface of the third stack portion disposed over a pinning layer 1340and the pinning layer 1340 disposed between the second stack portion1330 and the third stack portion 1350. Cap layer 704 is disposed overthe second surface of the third stack portion 1350.

The first stack portion 810 (i.e., a same stack portion as the firststack portion of MR element 800 of FIG. 8) includes a first plurality oflayers (here, 9 layers). Additionally, the second stack portion 1330includes a second plurality of layers (here, 8 layers), i.e., adifferent number of layers than the first plurality of layers. Further,the third stack portion 1350 includes a third plurality of layers (here,9 layers), i.e., a same number of layers as the first plurality oflayers and a different number of layers than the second plurality oflayers.

The second plurality of layers of the second stack portion 1330 includespinned layer structure 731, spacer layer 732 and free layer structure733. The second plurality of layers also includes a spacer layer 834 andpinned layer 735. The pinned layer structure 731 includes first pinnedlayer 731 a, second pinned layer 731 c and spacer layer 731 b.Additionally, free layer structure 733 includes first free layer 733 aand second free layer 733 b.

The pinned layer structure 731 is disposed over the pinning layer 720and the spacer layer 732 is disposed over the pinned layer structure731. Additionally, the free layer structure 733 is disposed over thespacer layer 732 and the spacer layer 834 is disposed over the freelayer structure 733. Further, the pinned layer 735 is disposed over thespacer layer 834.

The third plurality of layers of third stack portion 1350 includes apinned layer 1351, a spacer layer 1352 and a free layer structure 1353.The third plurality of layers also includes a spacer layer 1354, apinned layer structure 1355 and a pinning layer 1356. The free layerstructure 1353, which may be the same as or similar to free layerstructure 714 in the first stack portion 810 in some embodiments,includes first free layer 1353 a and second free layer 1353 b.Additionally, the pinned layer structure 1355, which may be the same asor similar to pinned layer structure 716 in first stack portion 810 insome embodiments, includes first pinned layer 1355 a, second pinnedlayer 1355 c and spacer layer 1355 b.

In embodiments, pinned layer 1351 may be a ferromagnetic pinned layer,spacer layer 1352 may be a nonmagnetic spacer layer and free layerstructure 1353 may be an unbiased free layer. Additionally, inembodiments, spacer layer 1354 may be a nonmagnetic spacer layer, pinnedlayer structure 1355 may include an SAF pinned layer structure or layerand pinning layer 1356 may be an antiferromagnetic pinning layer 1356.First free layer 1353 a of free layer structure 1353 may be aferromagnetic free layer and second free layer 1353 b of free layerstructure 1353 may be a ferromagnetic free layer. Additionally, firstpinned layer 1355 a of pinned layer structure 1355 may be ferromagneticpinned layer, second pinned layer 1355 c of pinned layer structure 1355may be a ferromagnetic pinned layer, and spacer layer 1355 b of pinnedlayer structure 1355 may be a nonmagnetic spacer layer.

The first stack portion 810 has a first substantially linear responsecorresponding to an applied magnetic field over a first magnetic fieldstrength range. Additionally, the second stack portion 1330 has a secondsubstantially linear response that is different than the firstsubstantially linear response. The second substantially linear responsecorresponds to the applied magnetic field over a second magnetic fieldstrength range. The third stack portion 1350 has a third substantiallylinear response that is different from both the first substantiallylinear response and the second substantially linear response. The thirdsubstantially linear response corresponds to an applied magnetic fieldbetween, or overlapping with, the first magnetic field strength rangeand the second magnetic field strength range. In one embodiment, thefirst substantially linear response has a first bias amplitude at about100 Oe, the second substantially linear response has a second biasamplitude of about 10 Oe and the third substantially linear response hasa third bias amplitude of about 50 Oe (i.e., between the first andsecond bias amplitudes). In embodiments, the respective bias amplitudescorrespond to magnetic field strengths at which the stack portions ofthe MR element are most responsive or sensitive to changes in magneticfield strength.

Similar to MR elements discussed in figures above, each of the stackportions 810, 1330, 1350 in MR element 1300 has at least onecharacteristic selected to result in the stack portions 810, 1330, 1350having their respective substantially linear responses (e.g., first,second, third, etc. substantially linear responses, like those whichoccur in regions 601 a, 601 b, 601 c shown in plot 600 of FIG. 6) to theapplied magnetic field.

In the illustrated embodiment, the thickness of spacer layer 813 infirst stack portion 810 may, for example, correspond to the at least onecharacteristic selected to result in the first stack portion 810 havingthe first substantially linear response. For example, the spacer layer813 may have a thickness selected (here, about 1.3 nm) to result in thefirst stack portion 810 having a first predetermined bias (e.g., a“strong” bias of about 200 Oe) which, in turn, may result in the firststack portion 810 having the first substantially linear response.

Additionally, in the illustrated embodiment, the thickness T2 of spacerlayer 834 in second stack portion 1330 may correspond to the at leastone characteristic selected to result in the second stack portion 1330having the second substantially linear response. For example, the spacerlayer 834 may have a thickness T2 selected to be a particular value(e.g., about 1.7 nm) to result in the second stack portion 1330 having asecond predetermined bias (e.g., a “very weak” bias of less than about10 Oe) which, in turn, may result in the second stack portion 1330having the second substantially linear response.

Further, in the illustrated embodiment, the thickness of spacer layer1352 in third stack portion 1350 may correspond to the at least onecharacteristic selected to result in the third stack portion 1350 havingthe third substantially linear response. For example, the spacer layer1352 may have a thickness selected (here, about 2.6 nm) to result in thethird stack portion 1350 having a third predetermined bias (e.g., a“moderate” bias of about 70 Oe) which, in turn, may result in the thirdstack portion 1350 having the third substantially linear response.

It is understood that other characteristics (e.g., materials, layerthicknesses, etc.) of the first, second and third stack portions 810,1330, 1350 may additionally or alternatively be selected to result inthe first, second and third stack portions 810, 1330, 1350 having theirrespective first, second and third substantially linear responses.

While MR elements including two or three so-called “stack portions” areshown in FIGS. 7, 8, 9, 12 and 13, it is understood that MR elementsaccording to the disclosure may include more than three stack portionsin some embodiments. Additionally, it is understood that the MR elementsshown in FIGS. 7, 8, 9, 12 and 13 are but five of many potentialconfigurations of MR elements in accordance with the disclosure. As oneexample, at least one of the stack portions (e.g., 1350) of MR element1300 may include a greater number of layers or a fewer number of layersthan that which is shown.

Additionally, while particular materials and thicknesses of layers in MRelements according to the disclosure are shown in FIGS. 7, 8, 9, 12 and13, it is understood that the materials and thicknesses of some layersmay be different than that which is shown, for example, to provide thefirst, second, third, etc. substantially linear responses of the first,second, third, etc. stack portions in the MR elements.

Further, while particular sequences of layers in MR elements accordingto the disclosure are shown in FIGS. 7, 8, 9, 12 and 13, it isunderstood that there can be other interposing layers, for example,other spacer layers, between any two or more of the layers shown, forexample, to provide the first, second, third, etc. substantially linearresponses of the first, second, third, etc. stack portions in the MRelements. Also, there can be other layers above or below the layersshown in FIGS. 7, 8, 9, 12 and 13. It is also understood that the MRelements can be formed in a variety of sizes and shapes. For example,the MR elements can be formed in a yoke shape such at that shown in FIG.15 through a manufacturing process, for example, in which the variouslayers of the MR elements are deposited, patterned and annealed.

It is also understood that the MR elements in accordance with thedisclosure may be coupled in a variety of arrangements, for example, aresistor divider arrangement, as shown in FIG. 14, or a bridgearrangement, as shown in FIG. 14A, which is described below. Further, itis understood that the MR elements in accordance with the disclosure maybe used in a variety of applications, including, but not limited tocurrent sensors responsive to an electrical current, proximity detectorsresponsive to proximity of a ferromagnetic object, for example, ferrousgear teeth, and magnetic field sensors responsive to a magnetic fieldexternal to the magnetic field sensor. One example magnetic field sensoris shown in FIG. 15, which is also described below.

Referring to FIG. 14, a resistor divider 1400 includes a resistor 1402and an MR element 1404, which may be the same as or similar to MRelements described in connection with figures above (e.g., 800, shown inFIG. 8) that are fabricated as a material stack. The resistor divider1400 is coupled to a voltage source 1401 and the resistor 1402 and theMR element 1404 may be driven by the voltage source 1401.

An output voltage (V_(OUT)) may be generated at the node 1400 a formedbetween the resistor 1402 and the MR element 1404 in response to anapplied magnetic field (e.g., a magnetic field as may be generated inresponse to motion of an object, such as ring magnet 1510, shown in FIG.15, as discussed below). In particular, changes in the applied magneticfield may cause the resistance of the MR element 1404 to change. As theresistance of the MR element 1404 changes, the output voltage at node1400 a may also change. The output voltage may have a magnitudeindicative of the applied magnetic field. In embodiments, the resistor1402 can be a substantially fixed resistor. Additionally, inembodiments, the resistor 1402 can be an MR element (i.e., a second MRelement).

Referring to FIG. 14A, a bridge arrangement (e.g., a Wheatstone bridgecircuit) 1450 includes MR elements 1452, 1454, 1456, 1458, one or morewhich may be the same as or similar to MR elements described inconnection with figures above (e.g., 800, shown in FIG. 8). The bridge1450 is coupled to a voltage source 1451 and each of magnetoresistanceelements 1452, 1454, 1456, 1458 may be driven by the voltage source1451.

A first output voltage (V_(OUT1)) may be generated at first voltage node1450 a formed between magnetoresistance elements 1452, 1454 in responseto an applied magnetic field. Additionally, a second output voltage(VP_(OUT2)) may be generated at a second voltage node 1450 b formedbetween magnetoresistance elements 1456, 1458 in response to the appliedmagnetic field. In particular, as the resistance of the MR elements1452, 1454, 1456, 1458 changes in response to the applied magneticfield, at least one of the first output voltage generated at the firstvoltage node 1450 a and the second output voltage generated at thesecond voltage node 1450 b may also change. A voltage difference betweenthe first output voltage (e.g., a first magnetic field signal) and thesecond output voltage (e.g., a second magnetic field signal) may beindicative of the applied magnetic field. In embodiments, the bridge1450 may include at least one substantially fixed resistor, and at leastone of the MR elements 1452, 1454, 1456, 1458 in bridge 1450 may bereplaced by the at least one substantially fixed resistor.

As illustrated above, the resistor divider 1400 of FIG. 14 and thebridge arrangement 1450 of FIG. 14A can provide an output signal (e.g.,a magnetic field signal) that is indicative of an applied magnetic fieldexperienced by the MR elements (e.g., 1404, shown in FIG. 14). It isunderstood that the resistor divider 1400 and the bridge arrangement1450 are but two of many potential arrangements of MR elements accordingto the disclosure.

Referring to FIG. 15, an example magnetic field sensor 1500 including aplurality of MR elements (here, four MR elements 1502, 1504, 1506, 1508)is shown. The MR elements 1502, 1504, 1506, 1508, which can be the sameas or similar to MR elements described in connection with figures above(e.g., 800, shown in FIG. 8), are each formed in the shape of a yoke anddisposed over a common substrate 1501 in the illustrated embodiment. Inembodiments, the MR elements 1502, 1504, 1506, 1508 can be coupled inresistor divider arrangements that may be the same as or similar to theresistor divider 1400 shown in FIG. 14. Additionally, in embodiments,the MR elements 1502, 1504, 1506, 1508 can be coupled in bridgearrangements (e.g., a Wheatstone bridge) that may be the same as orsimilar to bridge arrangement 1450 shown in FIG. 14A. It is understoodthat other configurations of the MR elements 1502, 1504, 1506, 1508 are,of course, possible. Additionally, it is understood that otherelectronic components (not shown), for example, amplifiers,analog-to-digital converters (ADC), and processors, i.e., an electroniccircuit, can be disposed over the substrate 1501 and coupled to one ormore of the MR elements 1502, 1504, 1506, 1508, for example, to processsignals (i.e., magnetic field signals) produced by the MR elements 1502,1504, 1506, 1508.

In the illustrated embodiment, the magnetic field sensor 1500 isdisposed proximate to a moving magnetic object, for example, a ringmagnet 1510 having alternative north and south magnetic poles. The ringmagnet 1510 is subject to motion (e.g., rotation) and the MR elements1502, 1504, 1506, 1508 of the magnetic field sensor 1500 may be orientedsuch that maximum response axes of the MR elements 1502, 1504, 1506,1508 are aligned with a magnetic field (e.g., an applied magnetic field)generated by the ring magnet 1510. In embodiments, the maximum responsesaxes of the MR elements 1502, 1504, 1506, 1508 may also be aligned witha magnetic field (e.g., a local magnetic field) generated by a magnet(not shown) disposed proximate to or within the magnetic field sensor1500. With such a back-biased magnet configuration, motion of the ringmagnet 1510 can result in variations of the magnetic field sensed by theMR elements 1502, 1504, 1506, 1508.

In embodiments, the MR elements 1502, 1504, 1506, 1508 are driven by avoltage source (e.g., 1451, shown in FIG. 14A) and configured togenerate one or more magnetic field signals (e.g., V_(out1), V_(out2),shown in FIG. 14A) in response to motion of the ring magnet 1510, e.g.,in a first direction of motion and in a second direction of motion thatis different than the first direction of motion. Additionally, inembodiments, one or more electronic components (e.g., an ADC) (notshown) on the magnetic field sensor 1500 are coupled to receive themagnetic fields signals and configured to generate an output signalindicative of position, proximity, speed and/or direction of motion ofthe ring magnet 1510, for example. In some embodiments, the ring magnet1510 is coupled to a target object, for example, a cam shaft in anengine, and a sensed speed of motion of the ring magnet 1510 isindicative of a speed of motion of the target object. The output signal(e.g., an output voltage) of the magnetic field sensor 1500 generallyhas a magnitude related to a magnitude of the magnetic field experiencedby the MR elements 1502, 1504, 1506, 1508.

In embodiments in which the MR elements 1502, 1504, 1506, 1508 areprovided as MR elements according to the disclosure (e.g., 800, shown inFIG. 8), the magnetic field sensor 1500 may have improved sensingaccuracy over embodiments in which the magnetic field sensor 1500includes conventional MR elements, for example, due to the increasedoperational range of magnetoresistance elements according to thedisclosure in comparison to conventional magnetoresistance elements. Inparticular, due to the increased operational range of magnetoresistanceelements according to the disclosure in comparison to conventionalmagnetoresistance elements, the magnetic field sensor 1500 may be ableto more accurately sense a wider (or increased) range of magnetic fieldstrengths than would otherwise be possible. For example, magnetic fieldstrengths that would otherwise saturate conventional MR elements may bedetected by MR elements according to the disclosure due to the increasedoperational range. This may provide for an increased number ofapplications in which MR elements according to the disclosure may besuitable (e.g., due to the increased range of magnetic field strengthswhich may be accurately detected using MR elements according to thedisclosure).

Additionally, in embodiments in which the MR elements 1502, 1504, 1506,1508 are provided as MR elements according to the disclosure (e.g., 800,shown in FIG. 8), and the magnetic field sensor 1500 includes electroniccomponents (e.g., ADCs) coupled to receive magnetic field signals fromthe MR elements 1502, 1504, 1506, 1508 and configured to generate theoutput signal of the magnetic field sensor 1500, operationalrequirements of the electronic components (e.g., so-called “front endelectronics” or “signal processing electronics”) may, for example, bereduced in comparison to embodiments in which the magnetic field sensor1500 includes conventional magnetoresistance elements.

For example, as is known, an ADC has a dynamic range corresponding to arange of signal amplitudes or strengths which the ADC can resolve (i.e.,process). If an analog input signal has an amplitude that is greaterthan an upper threshold of the dynamic range, or an amplitude that isless than a lower threshold of the dynamic range, the ADC may not beable to accurately convert the analog signal into a correspondingdigital signal. As discussed above, MR elements according to thedisclosure have at least a first substantially linear response resultingin a first sensitivity level to changes in magnetic field strength and asecond substantially linear response resulting in a second sensitivitylevel to changes in magnetic field strength. As also discussed above, atleast one characteristic in the at least first and second stack portionsof the MR elements according to the disclosure may be selected toprovide the first and second substantially linear responses, and thefirst and second sensitivity levels. In other words, the first andsecond sensitivity levels of the MR elements may be selected based uponthe at least one characteristic selected in the first and second stackportions of the MR elements.

In embodiments, the first and second sensitivity levels of the MRelements according to the disclosure may be selected to be reduced incomparison to the single sensitivity level of conventional MR elementsand, as a result, an output of MR elements according to the disclosure(e.g., V_(OUT), shown in FIG. 14) may increase more gradually or at asmall rate (and have a reduced upper threshold) in comparison to anoutput of conventional MR elements. It follows than an ADC coupled toreceive an output of MR elements according to the disclosure may have adynamic range requirement which is reduced in comparison to a rangerequirement of an ADC coupled to receive an output of conventional MRelements. As a result of the foregoing, in embodiments in which themagnetic field sensor 1500 includes MR elements according to thedisclosure, the magnetic field sensor 1500 may be able to use ADCs thathave a reduced dynamic range (and that may be less costly) in comparisonto embodiments in which the magnetic field sensor 1500 includesconventional MR elements.

It is understood that the dynamic range of an ADC is but one exampleoperational parameter of the ADC which may benefit from the variouscharacteristics associated with MR elements according to the disclosure.It is also understood than an ADC is but one example electricalcomponent that may be used in the magnetic field sensor 1500, and whichmay benefit from the various characteristics associated with MR elementsaccording to the disclosure.

In embodiments, MR elements according to the disclosure may also providefor a magnetic field sensor 1500 having a reduced number of electricalcomponents (e.g., signal processing components) compared, for example,to a magnetic field sensor 1500 including conventional MR elements. Forexample, in embodiments in which the magnetic field sensor 1500 includesconventional MR elements and is configured to sense applied magneticfields having a plurality of magnetic field strength ranges (e.g., −10 Gto 10 G, −100 G to 100 G and −300 G to 300 G), the magnetic field sensor1500 may require a corresponding plurality of ADCs. In contrast, inembodiments in which the magnetic field sensor 1500 includes MR elementsaccording to the disclosure and is configured to sense the plurality ofmagnetic field strength ranges, the magnetic field sensor 1500 mayinclude a fewer or reduced number of ADCs than the plurality of magneticfield strength ranges. In one embodiment, the foregoing is due to MRelements according to the disclosure having an increased operationalrange compared to conventional MR elements. In particular, with MRelements according to the disclosure as signals (e.g., magnetic fieldsignals) become larger, the signals may be reduced (or even muted insome embodiments) but still usable for signal processing (e.g., due tothe MR elements not being forced into saturation).

While the magnetic field sensor 1500 is shown and described as a motiondetector to motion rotation of the ring magnet 1510 in the illustratedembodiment, it is understood that other magnetic field sensors, forexample, current sensors, may include one or more of the MR elementsaccording to the disclosure.

Additionally, while the MR elements 1502, 1504, 1506, 1508 are shown anddescribed as formed in the shape of a yoke, it is understood that insome embodiments the MR element may instead be formed in the shape of astraight bar or a number of other shapes. For example, for a GMRelement, the stack portions (e.g., first and second stack portions) ofthe GMR element may form a yoke shape. In contrast, for a TMR element,in some embodiments, selected portions of the TMR element (e.g., freelayers of the stack portions) may have a yoke shape and remainingportions of the TMR element may have another shape (e.g., a straightbar). In some embodiments, one or more dimensions (e.g., a length, widthand height) of the yoke or other shaped MR element may be based upon anumber of layers and/or a thickness of the layers in the MR element.

Referring now to FIG. 16, an MR element 1600 (e.g., a double pinned MRelement) is deposited or otherwise provided upon a substrate 1602 (e.g.,a silicon substrate) and includes a plurality of layers (here, twelvelayers). The plurality of layers includes a nonmagnetic seed layer 1604disposed over the substrate 1602, a material stack 1606 (or stackportion) disposed over the nonmagnetic seed layer 1604 and a nonmagneticcap layer 1608 disposed over the material stack 1606.

The material stack 1606 includes an antiferromagnetic pinning layer 1610disposed over the nonmagnetic seed layer 1604, a ferromagnetic pinnedlayer 1612 disposed over the antiferromagnetic pinning layer 1610 and anonmagnetic spacer layer 1614 disposed over the ferromagnetic pinnedlayer 1612. A free layer structure 1616 may be disposed over thenonmagnetic spacer layer 1614, a nonmagnetic spacer layer 1618 disposedover the free layer 1616 and a pinned layer structure 1620 disposed overthe nonmagnetic spacer layer 1618. The free layer structure 1616includes a first ferromagnetic free layer 1616 a and a secondferromagnetic free layer 1616 b disposed over the first ferromagneticfree layer 1616 a. Additionally, the pinned layer structure 1620includes a first ferromagnetic pinned layer 1620 a, a secondferromagnetic pinned layer 1620 c, and a nonmagnetic spacer layer 1620 bdisposed therebetween.

The material stack 1606 additionally includes an antiferromagneticpinning layer 1622 disposed between the pinned layer structure 1620 andthe cap layer 1608.

Each of the plurality of layers in the prior art MR element 1600includes one or more respective materials (e.g., magnetic materials) andhas a respective thickness, as shown. Materials of the layers are shownby atomic symbols. Additionally, thicknesses of the layers are shown innanometers (nm).

In general, magnetic materials can have a variety of magneticcharacteristics and can be classified by a variety of terms, including,but not limited to, ferromagnetic, antiferromagnetic, and nonmagnetic.Detailed descriptions of the variety of types of magnetic materials arenot made herein. However, let it suffice here to say, that aferromagnetic material (e.g., CoFe) is a material in which magneticmoments of atoms within the material tend to, on average, align to beboth parallel and in a same direction, resulting in a nonzero netmagnetic magnetization of the material. Additionally, a nonmagnetic ordiamagnetic material (e.g., Ta, Cu or Ru) is a material which tends topresent an extremely weak magnetization that is opposite andsubstantially proportional to a magnetic field to which the material isexposed and does not exhibit a net magnetization. Further, anantiferromagnetic material (e.g., PtMn) is a material in which magneticmoments of atoms within the material tend to, on average, align to beparallel but in opposite directions, resulting in a zero-netmagnetization.

Within some of the plurality of layers in MR element 1600, arrows areshown that are indicative of magnetization directions of the layers whenthe MR element 1600 experiences a nominal (or zero) applied magneticfield. Arrows coming out of the page are indicated as dots withincircles and arrows going into the page are indicated as crosses withincircles.

Detailed descriptions of the various magnetization directions are notprovided in this document. However, let it suffice here to say that, asis known in the art, some MR elements (e.g., GMR and TMR elements)operate with spin electronics (i.e., electron spins) where theresistance of the MR elements is related to the magnetization directionsof certain layers in the MR elements.

The MR element 1600 may have a maximum response axis to magnetic fieldswhich is parallel to a surface 1624 of the substrate 1602 over which theMR element 1600 is deposited. Additionally, the MR element 1600 has aresistance that changes in response to the applied magnetic field in adirection of the maximum response axis of the MR element 200 over alimited range of magnetic field strengths.

In embodiments, MR element 1600 may include a first stack portion 1626.Stack portion 1626 may comprise a first plurality of layers, such aslayers 1604-1618. The first stack portion 1626 may have a substantiallylinear response (i.e. a substantially linear change in electricalresistance) to an applied magnetic field over a first magnetic fieldrange.

First stack portion 1626 may comprise a first spacer layer (e.g. spacerlayer 1614) having a first thickness. Although spacer layer 1614 iscomprises the material Ru and having thickness of 0.1 to 5.0 nm, othermaterials (such as Rh) and thicknesses may be used.

Although shown as having a different number of layers, in otherembodiments, stack portions 1626 and 1628 may each have the same numberof layers.

Referring now to FIG. 17, another example of an MR element 1700 (e.g., aso-called “dual double pinned MR element”) is deposited or otherwiseprovided upon a substrate 1701 and includes a plurality of layers. Theplurality of layers includes a nonmagnetic seed layer 1702 disposed overthe substrate 1701, a first material stack portion 1710 (also sometimesreferred to herein as “a first stack portion”) disposed over thenonmagnetic seed layer 1702 and an antiferromagnetic pinning layer 1720disposed over the first material stack portion 1710. The MR element 1700also includes a second material stack portion 1730 (also sometimesreferred to herein as “a second stack portion”) disposed over theantiferromagnetic pinning layer 1720 and a nonmagnetic cap layer 1704disposed over the second material stack portion 1730.

The first stack portion 1710, which contains a similar ordering orarrangement of layers as the stack portion 1606 (see FIG. 16) less asecond antiferromagnetic pinning layer, includes an antiferromagneticpinning layer 1711 disposed over the nonmagnetic seed layer 1702 and aferromagnetic pinned layer 1712 disposed over the antiferromagneticpinning layer 1711. The first stack portion 1710 also includes anonmagnetic spacer layer 1713 disposed over the ferromagnetic pinnedlayer 1712 and a free layer structure 1714 disposed over the nonmagneticspacer layer 1713. The free layer structure 1714 includes a firstferromagnetic free layer 1714 a and a second ferromagnetic free layer1714 b disposed over the first ferromagnetic free layer 1714 a.

The first stack portion 1710 further includes a nonmagnetic spacer layer1715 disposed over the free layer structure 1714 and a pinned layerstructure 1716 disposed over the nonmagnetic spacer layer 1715. Thepinned layer structure 1716 includes a first ferromagnetic pinned layer1716 a, a second ferromagnetic pinned layer 1716 c and a nonmagneticspacer layer 1716 b disposed therebetween.

The second stack portion 1730, which is similar to the first stackportion 1710 but includes layers that are in a substantially reverseorder or arrangement as the layers which are shown in first stackportion 1710 with respect to the seed layer 1702, includes a pinnedlayer structure 1731 disposed over the antiferromagnetic pinning layer1720, a nonmagnetic spacer layer 1732 disposed over the pinned layerstructure 1731 and a free layer structure 1733 disposed over thenonmagnetic spacer layer 1732. The pinned layer structure 1731 includesa first ferromagnetic pinned layer 1731 a, a second ferromagnetic pinnedlayer 1731 c and a nonmagnetic spacer layer 1731 b disposedtherebetween. Additionally, the free layer structure 1733 includes afirst ferromagnetic free layer 1733 a and a second ferromagnetic freelayer 1733 b, disposed over the first ferromagnetic free layer 1733 a.

The second stack portion 1730 also includes a nonmagnetic spacer layer1734 disposed over the free layer structure 1733, a ferromagnetic pinnedlayer 1735 disposed over the nonmagnetic spacer layer 1734 and anantiferromagnetic pinning layer 1736 disposed over the ferromagneticpinned layer 1735. A nonmagnetic cap layer 1704 is disposed over theantiferromagnetic pinning layer 1736.

Each of the layers in prior art MR element 1700 includes one or morerespective materials (e.g., magnetic materials) and has a respectivethickness, as shown. Materials of the layers are shown by atomicsymbols. Additionally, thicknesses of the layers are shown innanometers. In other embodiments, the material and thicknesses of thelayers in MR element 1700 may be replaced with other materials andthicknesses.

Arrows are shown that are indicative of magnetization directions of thelayers when the MR element 1700 experiences a nominal (or zero) appliedmagnetic field. Arrows coming out of the page are indicated as dotswithin circles and arrows going into the page are indicated as crosseswithin circles.

Detailed descriptions of the various magnetization directions are notprovided in this document. However, let it suffice here to say that, asis known in the art, some MR elements (e.g., GMR and TMR elements)operate with spin electronics (i.e., electron spins) where theresistance of the MR elements is related to the magnetization directionsof certain layers in the MR elements.

The MR element 1700 has a maximum response axis to magnetic fields whichis parallel to a surface of the substrate 1701 over which the MR element1700 is deposited, as indicated by arrow 1799. Additionally, the MRelement 1700 has an electrical resistance that changes generally inproportion to an applied magnetic field in a direction of the maximumresponse axis of the MR element 1700 over a limited range of magneticfield strengths.

Referring to FIG. 18, a graph 1800 includes a waveform 1802 representingthe transfer function of an MR element (such as MR element 1600 or 1700)in the presence of an applied magnetic field. The horizontal axisrepresents arbitrary units of magnetic field strength of the appliedmagnetic field and the vertical axis represents resistance of the MRelement in Ohms.

When the MR element experiences a magnetic field with zero strength, theresistance of the MR element is at an intermediate value, as shown bypoint 1804. As the strength of the external magnetic field increases,the resistance of the MR element decreases as shown, for example, bypoint 1806. Conversely, as the strength of the applied magnetic fieldincreases in the other direction, the resistance of the MR elementincreases as shown, for example, by point 1808.

The graph 1800 is divided into three regions: low sensitivity regions1810 and 1812 where the resistance of the MR element is relativelyinvariable with changes to the strength of the applied magnetic field(i.e. where the slope of the resistance curve 1802 is relatively closeto zero), and high sensitivity region 1814 where the resistance of MRelement has a relatively large slope (i.e. where the slope of theresistance curve 1802 is relatively distant from zero). Changing thematerial and thickness of the spacer regions, as discussed above, mayaffect the size and offset (right or left) of the high sensitivityregion 1814 and the shape of resistance curve 1802 within highsensitivity region 1814. For example, changing the thickness of Copperlayer 1732 may change the proportion of high and low sensitivity. Asanother example, changing the material and thickness of layers 1734and/or 1713 may change the sensitivities in the high and low sensitivityzones of the MR element's transfer function.

Referring to FIG. 19, graph 1900 shows a series of waveforms 1902representing the resistance of a double pinned MR element with differentthicknesses of the spacer layer 1732 of the low sensitivity stackportion (e.g. stack portion 1730 in FIG. 17). Curve A illustrates thecase where the spacer layer 1732 of the low sensitivity stack portion1730 has the same thickness and material as the spacer layer 1715 of thehigh sensitivity stack portion (e.g. stack portion 1710). Curve Billustrates the case where the spacer layer 1730 of the low sensitivitystack portion 1730 has a thickness that is about 25% higher of that ofthe spacer layer 1730 of the high sensitivity stack portion 1730. Asshown, increasing the thickness of the spacer layer 1732 of the lowsensitivity stack portion 1730 may result in curve B having a largersensitivity and a smaller linear range (e.g. between points 1904 and1906) that than of curve A (e.g. between points 1908 and 1910). Otherones of the curves show other percentages and resulting different linearranges.

Referring to FIG. 20, graph 2000 shows a series of waveforms 2002representing the resistance of a double pinned MR element with differentthicknesses of the spacer layer 1715 of the high sensitivity stackportion (e.g. stack portion 1710 in FIG. 17). Curve C illustrates thecase where the spacer layer 1715 of the high sensitivity stack portion1710 has the same thickness and material as the spacer layer of the lowsensitivity stack portion (e.g. stack portion 1730). Curve D illustratesthe case where the spacer layer 1715 of the high sensitivity stackportion 1710 has a thickness that is about 25% lower of that of thespacer layer 1732 of the low sensitivity stack portion 1710. As shown,reducing the thickness of the spacer layer 1715 of the high sensitivitystack portion 1710 may result in curve D having a lower sensitivity anda larger linear range (e.g. between points 2004 and 2006) that than ofcurve C (e.g. between points 2008 and 2010).

The MR element 1700 in FIG. 17 may also have varying linear range andsensitivity based on the thickness of spacer layers 1715 and 1732.Reducing the thickness of spacer layer 1715 and/or spacer layer 1732 mayresult in MR element 1700 having lower sensitivity and larger linearrange.

As described above and as will be appreciated by those of ordinary skillin the art, embodiments of the disclosure herein may be configured as asystem, method, or combination thereof. Accordingly, embodiments of thepresent disclosure may be comprised of various means including hardware,software, firmware or any combination thereof.

Having described preferred embodiments, which serve to illustratevarious concepts, structures and techniques, which are the subject ofthis patent, it will now become apparent to those of ordinary skill inthe art that other embodiments incorporating these concepts, structuresand techniques may be used. Additionally, elements of differentembodiments described herein may be combined to form other embodimentsnot specifically set forth above.

Accordingly, the scope of the patent should not be limited to thedescribed embodiments but rather should be limited only by the spiritand scope of the following claims.

The invention claimed is:
 1. A magnetoresistance element deposited upona substrate, comprising: a first stack portion comprising a firstplurality of layers, wherein the first plurality of layers comprises: afirst pinned layer structure; a first free layer structure; and a firstspacer layer in contact with the first pinned layer structure and thefirst free layer structure and having a first thickness and a firstmaterial selected to result in the first stack portion having a firstsensitivity to the applied magnetic field; a second stack portioncomprising a second plurality of layers, wherein the second stackportion is disposed over the first stack portion, wherein the secondplurality of layers comprises: a second pinned layer structure; a secondfree layer structure; and a second spacer layer in contact with thesecond pinned layer structure and the second free layer structure andhaving a second thickness and a second material selected to result inthe second stack portion having a second sensitivity to the appliedmagnetic field, wherein the first thickness is different than the secondthickness resulting in the first sensitivity being different than thesecond sensitivity, wherein the first sensitivity corresponds to a firstchange in a resistance of the magnetoresistance element and the secondsensitivity corresponds to a second change in the resistance of themagnetoresistance element; and an electroconductive layer being indirect contact with the second stack portion and being in direct contactwith the first stack portion, wherein the first plurality of layers andthe second plurality of layers each consist of a different number oflayers, wherein the first stack portion and the second stack portioneach consist of a different number of layers.
 2. The magnetoresistanceelement of claim 1, wherein the first and second spacer layers arecomprised of Copper (Cu).
 3. The magnetoresistance element of claim 1,wherein the first and second spacer layers are comprised of insulatinglayers.
 4. The magnetoresistance element of claim 1, wherein the firstand second spacer layers are comprised of MgO.
 5. The magnetoresistanceelement of claim 1, wherein the first thickness of the first spacerlayer is about 0.1 nm or greater.
 6. The magnetoresistance element ofclaim 1, wherein the first and second pinned layer structures eachinclude one respective pinned layer.
 7. The magnetoresistance element ofclaim 1, wherein the first and second pinned layer structures eachcomprise a respective synthetic antiferromagnetic (SAF) structure. 8.The magnetoresistance element of claim 1, wherein the magnetoresistanceelement comprises one or more of a giant magnetoresistance (GMR)element, a magnetic tunnel junction (MTJ) element, a tunnelingmagnetoresistance (TMR) element, or a spin valve.
 9. Themagnetoresistance element of claim 1, wherein the magnetoresistanceelement is provided in a magnetic field sensor.
 10. Themagnetoresistance element of claim 1, wherein the electroconductivelayer is a pinning layer.
 11. The magnetoresistance element of claim 1,wherein the electroconductive layer is a platinum manganese (PtMn). 12.The magnetic field sensor of claim 1, wherein the first and secondsubstantially linear responses are provided at least in part from theelectroconductive layer.
 13. The magnetoresistance element of claim 1,wherein the first thickness differs from the second thickness by about25%.
 14. The magnetoresistance element of claim 1, wherein the secondstack portion comprises a single pinning layer and a single pinnedlayer, wherein the second stack portion is a double-pinned arrangement,wherein the single pinning layer pins the single pinned layer and theelectroconductive layer pins the second pinned layer structure togetherto form the double-pinned arrangement in the second stack portion,wherein the first stack portion is single-pinned arrangement, whereinthe electroconductive layer pins the first pinned layer structure toform the single-pinned arrangement in the first stack portion.
 15. Themagnetoresistance element of claim 1, wherein the first and secondspacer layers are comprised of conductive layers.
 16. Themagnetoresistance element of claim 15, wherein the second thickness ofthe second spacer layer is 0.1 nm or greater.
 17. A magnetic fieldsensor comprising: one or more magnetoresistance elements deposited upona substrate, one of the magnetoresistance elements comprising: a firststack portion comprising a first plurality of layers, wherein the firstplurality of layers comprises: a first pinned layer structure; a firstfree layer structure; and a first spacer layer in contact with the firstpinned layer structure and the first free layer structure and having afirst thickness and a first material selected to result in the firststack portion having a first sensitivity to the applied magnetic field;a second stack portion comprising a second plurality of layers, whereinthe second stack portion is disposed over the first stack portion, andwherein the second plurality of layers comprises: a second pinned layerstructure; a second free layer structure; a second spacer layer incontact with the second pinned layer structure and the second free layerstructure and having a second thickness selected to result in the secondstack portion having a second sensitivity to the applied magnetic field,wherein the first thickness is different than the second thicknessresulting in the first sensitivity being different than the secondsensitivity, wherein the first sensitivity corresponds to a first changein a resistance of the magnetoresistance element and the secondsensitivity corresponds to a second change in the resistance of themagnetoresistance element; and an electroconductive layer being indirect contact with the second stack portion and being in direct contactwith the first stack portion, wherein the first plurality of layers andthe second plurality of layers each consist of a different number oflayers, wherein the first stack portion and the second stack portioneach consist of a different number of layers.
 18. The magnetic fieldsensor of claim 17 wherein the first spacer layer comprises MgO.
 19. Themagnetic field sensor of claim 17, wherein the second spacer layercomprises copper and the second thickness of the second spacer layer is2.4 nm or greater.
 20. The magnetic field sensor of claim 17, whereinthe second spacer layer comprises MgO.
 21. The magnetic field sensor ofclaim 17, wherein the electroconductive layer is a pinning layer. 22.The magnetic field sensor of claim 17, wherein the electroconductivelayer is a platinum manganese (PtMn).
 23. The magnetic field sensor ofclaim 17, wherein the first and second substantially linear responsesare provided at least in part from the electroconductive layer.
 24. Themagnetic field sensor of claim 17, wherein the first thickness differsfrom the second thickness by about 25%.
 25. The magnetic field sensor ofclaim 17, wherein the second stack portion comprises a single pinninglayer and a single pinned layer, wherein the second stack portion is adouble-pinned arrangement, wherein the single pinning layer pins thesingle pinned layer and the electroconductive layer pins the secondpinned layer structure together to form the double-pinned arrangement inthe second stack portion, wherein the first stack portion issingle-pinned arrangement, wherein the electroconductive layer pins thefirst pinned layer structure to form the single-pinned arrangement inthe first stack portion.
 26. The magnetic field sensor of claim 17wherein the first spacer layer comprises copper.
 27. The magnetic fieldsensor of claim 26 wherein the first thickness of the first spacer layeris 2.4 nm or greater.
 28. A magnetic field sensor, comprising: amagnetoresistance element configured to generate first and secondsubstantially linear responses to an applied magnetic field, wherein thefirst and second substantially linear responses have substantially zerooffset with respect to an expected response of the magnetoresistanceelement at an applied magnetic field strength of about zero Oersteds;wherein the magnetoresistance element comprises: a first stack portioncomprising a first plurality of layers, wherein the first plurality oflayers comprises: a first pinned layer structure; a first free layerstructure; and a first spacer layer in contact with the first pinnedlayer structure and the first free layer structure and having a firstthickness and a first material selected to result in the first stackportion having a first sensitivity to the applied magnetic field; asecond stack portion comprising a second plurality of layers, whereinthe second stack portion is disposed over the first stack portion,wherein the second plurality of layers comprises: a second pinned layerstructure; a second free layer structure; a second spacer layer incontact with the second pinned layer structure and the second free layerstructure and having a second thickness and a second material selectedto result in the second stack portion having a second sensitivity to theapplied magnetic field, wherein the first thickness is different thanthe second thickness resulting in the first sensitivity being differentthan the second sensitivity, wherein the first sensitivity correspondsto a first change in a resistance of the magnetoresistance element andthe second sensitivity corresponds to a second change in the resistanceof the magnetoresistance element; and an electroconductive layer beingin direct contact with the second stack portion and being in directcontact with the first stack portion, wherein the first plurality oflayers and the second plurality of layers each consist of a differentnumber of layers, wherein the first stack portion and the second stackportion each consist of a different number of layers.
 29. The magneticfield sensor of claim 28, wherein the first thickness differs from thesecond thickness by about 25%.
 30. The magnetic field sensor of claim28, wherein the second stack portion comprises a single pinning layerand a single pinned layer, wherein the second stack portion is adouble-pinned arrangement, wherein the single pinning layer pins thesingle pinned layer and the electroconductive layer pins the secondpinned layer structure together to form the double-pinned arrangement inthe second stack portion, wherein the first stack portion issingle-pinned arrangement, wherein the electroconductive layer pins thefirst pinned layer structure to form the single-pinned arrangement inthe first stack portion.